Fatty Acid Degradation

Transcription

1 Fatty Acid Degradatin Fat is stred as triglycerides (TAGs) Perlipin: Enzyme that digests the envelpe f prtein surrunding the glbule f fat. Hrmne Sensitive Lipase (HSL): Digests the actual fat glbule. Bth HSL and Perilipin must be phsphrylated t be ACTIVE In the adipcytes 1. Perilipin digests the prtein envelpe surrunding the TAG 2. HSL clips a FA frm C1 r C3 s nw TAG DAG 3. Other lipases wrk t turn DAG 3 Free Fatty Acids (FFA) & glycerl 4. Glycerl is sent t the liver Liver is the ONLY rgan with glycerl kinase Glycerl in the liver is phsphrylated by GK t glycerl 3 phsphate G3P can nw be used in glucnegenesis t make glucse 5. FFA are released frm the adipcytes int the bld stream and attach t albumin fr transprt We ve arrived in the liver 6. Once at the liver, FFA are released frm albumin and diffuses acrss the cell membrane f the hepatcytes 7. Once inside the cell, lipids are rapidly cmpartmentalized FFA are NOT FOUND in a healthy cell they are txic in their amphteric state Can have detergent like effects n the cell membrane (disruptin f cell membrane) s therefre they must be activated t prevent this. Albumin Large plasma prtein Used t carry hydrphbic mlecules thrugh bld VERY SOLUBLE ultimately makes anything it attaches t sluble Key player in smtic maintenance Activatin f FA- Length Specific Occurs in cytsl f Hepatcyte Always an Acetyl-cA synthetase but the type (VLC, LC, MC, SC) will depend n the length f the FA itself and where in the cell the FA can be digested Perxismes ONLY digest VLCFA Mitchndria can ONLY digest LCFA & MC Acetyl-cA synthe tase requires ATP & CA ATP A M P +PPi (similar t glyclysis requires 2 phsphate bnds t activate) LAG fr glucnegenesis Fatty acid Fatty Acyl CA via acetyl-ca synthetase Length f FA Lcatin Acetyl ca synthetase Very Lng Chain Fatty Acid C Perxismes VLCFA Acyl-CA synthetase Lng Chain Fatty Acid C Mitchndria LCFA Acyl C-A synthetase Medium Chain Fatty Acid 6-12 C Mitchndria MC Acyl-CA synthetase Shrt Chain Fatty Acid 2-4 C Cytplasm SC Acyl-CA synthetase -Nmenclature f future enzymes (nted by **) are named in a similar fashin table will nt be repeated.

2 Fatty Acyl CA mves int the mitchndria--- Frm this pint ut we are ging t use 16C Palmitate as an ex/ Requires a series f steps t mve the activated fatty acyl ca acrss the mitchndrial membrane Activated Fatty Acyl CA runs thrugh Carnitine Acyl Transferase I (CAT I/CPTI) Lcated in the uter mitchndrial membrane CAT I swaps the CA ut fr a carnitine mlecule Exchange fr carnitine allws fatty acyl carnitine t be translcated int mitchndria via a carnitine transprter prtein CAT I is inhibited by malnyl ca (reactant fr FA synthesis fund in cytsl) yu dn t want t break dwn what yu re trying t make s sufficient levels f malnyl ca will inhibit the CAT I shuttle frm bringing in FA t the mitchndria fr degradatin. Lw energy activates CAT I by inhibiting synthesis f FA via malnyl ca Nw fatty-acyl carnitine is inside the mitchndrial matrix. CAT II, lcated n the inner mitchndrial membrane swaps carnitine ut fr a CA grup s nw we have a fatty-acyl-ca mlecule INSIDE the mitchndrial matrix Withut the shuttle it s impssible t get fatty-acyl CA shuttled int the membrane. Side Nte: Remember that carnitine is nly used t get FA thrugh the MITOCHONDRIAL membrane, s this methd f transprt is nly used n LCFA,MCFA, SCFA CPTI is technically used fr LCFA ONLY! 16 C Palmitate is ur standard FA Other derivatives f acyl-transferases are length specific (medium and shrt) s MCFA/SCFA are nt subject t inhibitin by malnyl ca. & can crss uter mitchndrial membrane w/ help VCLFA are degraded in the perxismes int LCFA which are then exprted ut f the perxisme and int the mitchndria via this carnitine mechanism Inf n Carnitine Sle transmembrane Carrier f LCFA--- HIGHLY SOLUBLE Carnitine can be btained frm meat prducts in ur diet Can als be synthesized frm lysine and methinine in liver/kidney (NOT in skeletal muscle/heart) Can be referred t as Vitamin B T

3 S nw ur Fatty Acyl CA is in the mitchndrial matrix time fr β xidatin Prducts f β xidatin: FADH 2, NADH 2, Acetyl CA -N direct allsteric regulatin f any step in β xidatin -2 Cs are remved per cycle s fr a 16C FA β xidatin must spiral (repeat itself) a ttal f 7x t yield 8 fragments - The Fatty acyl ca will re-enter the spiral until it has been fully degraded. S fr a 16 C FA 7 FADH 2, 7NADH, & 8 Acetyl-CA mlecules --Big Picture: Lts f energy can be btained frm all the NADH, FADH 2 prduced. Acetyl CA can be used in the TCA cycle r fr ketne prductin (liver nly) ( Remember FA give yu mre ATP per carbn than carbs d= better surce f energy ) Knw the 5 Majr reactins: Dehydrgenatin **, Ismerizatin, Hydratin, Dehydrgenatin, & Thilysis Ismerizatin via Enlase nly majr because yu need t knw all duble bnds are naturally in cis cnfiguratin. Ismerizatin must ccur t create the trans cnfiguratin fr every duble bnd. Okay s we ve shwn the prcess fr EVEN chained FA nw what d we d if we have an dd chain FA? Break dwn FA as yu wuld in β xidatin but instead f yur end prducts being 2-acetyl CA mlecules yu have acetyl CA (2C) and prpinyl CA (3C)

4 still ccurs in mitchndrial hepatcyte! Side Nte: Phyntanic acid frm alpha xidatin prduces a tn f prpinyl CA 1. Carbxylatin- ABC required via prpinyl CA carbxylase 3C 4C 2. Ismer cnversin D L 3. Rearrangement f carbns via MM-CA mutase REQUIRES VIT. B12 - Mutase reactin is 1 f 2 reactins that require Vitamin B 12 -Succinyl CA can enter the TCA cycle Anther kind f FA xidatin: Omega (ω) xidatin Occurs in the ER (micrsmal) Terminal methyl grup (w/ ω carbn) n FA can be xidized via ER LOCATED dehydrgenase f Cyt P450 (requires O 2 and NADPH) Turns CH 3 int OH CH 2 (Creates a 2 nd COOH grup) New prduct can nw under g beta xidatin (as a MCFA) NO feedback regulatin f ER xidatin Rate is cntrlled by availability f substrate Used t remve txic FA-like cmpunds (xenbitics) FA Oxidatin in the PEROXISOMES VLCFA α Oxidatin: Branched FA

5 VCLFA Oxidatin-- β xidatin VCLFA = 22 C r lnger Difference between mitchndrial & perxismal β xidatin Mitchndria: 1 st step generates: FADH 2 generates energy Perxismes: 1 st step generates: FADH 2 which is then xidized by O 2 creating H 2 O 2 N energy generated in 1 st step by perxismes Perxismes break dwn FA until they reach MCFA (4-6 C in which pint they are transferred t the mitchndria Any acetyl C-A generated is transferred t the mitchndria α Oxidatin: LC Branched FA Phyntanic Acid (20C)- methyl grup in beta carbn therefre can t be degraded via beta xidatin Multi-methyl branched FA fund in green veggies als fund in ruminant milk α Oxidatin requires Vitamin C 1 st step is the hydrxylatin f the α carbn (if this is defective= Refsum s disease) Hydrxylatin perfrmed by phytanyl CA-hydrxylase Hydrxylatin, decarbxylatin, xidatin, activatin C1 is released in decarbxylatin-> 19C pristanic acid Yields 3 acetyl-ca, 3 Prpinyl-CA, and Is-butyrl CA Acetyl CA TCA cycle Prpinyl CA ODD NUMBER beta xidatin in mitchndria Large number f prpinyl ca generated frm LC branched fatty acids Ketne Metablism- Alternate Fuel fr Cells Liver mitchndria can cnvert acetyl CA derived frm FA int ketne bdies (synthesis) Oxidatin f ketne bdies must ccur in mitchndria f OTHER TISSUES (NOT in liver r RBCs) Ketne bdies

6 Acetacetate (true ketne) 3-hydrxybutyrate (nt a true ketne) Acetne (True ketne) There s always must mre 3-hydrxybutyrate: acetacetate (4:1) Imprtant surce f energy fr peripheral tissues. Lw insulin w/ High glucagn will stimulate prductin f ketnes Sluble in aqueus slutins (dn t need t be carried) lw pka ptential fr danger= ketacidsis Ketgenesis ccurs in mitchndrial matrix f the hepatcyte Driven by acetyl-ca prductin frm beta xidatin (n substrate= n ketgenesis) HMG-CA synthase rate limiting enzyme f ketgenesis nly fund in the liver - Stimulated by fasting and insulin deficiency ( Nt technically hrmnally cntrlled by insulin insulin desn t activate a phsphatase etc) Nte: HMG CA in this pathway IS NOT the HMG CA used in the synthesis f chlesterl. These 2 HMG CA NEVER MIX HMG-CA lyase clips an acetyl CA ff Acetacetate is really unstable b/c f high energy bnd which is why it spntaneusly decarbxylates t acetne. Its instability als can be accunted fr in the 4:1 rati (there are 4 beta hydrxybutyrate fr every 1 acetacetate present) -Rati maintained by D-Beta hydrxybutyrate dehydrgenase Other things t cnsider: CAT 1 must be active during starvatin yu need t acetyl ca t create ketnes Acetyl-CA cmes frm beta xidatin (FA int mitchndria) Fr FA t cme int mitchndria HSL must be phsphrylated =active (due t glucagn) Malnyl ca levels must be lw (malnyl ca is invlved in FA synthesis when insulin is high) Als inhibits CAT I: Lw malnyl CA active CAT I Beta xidatin acetyl-ca In starvatin- FFA s, acetacetate and glucse are very cnstant. Only levels f beta hydrxybutyrate increase with starvatin (4C mlecule and there is 4x mre present) We ve made ketnes s wh can use them and hw d they use them

7 Acetne is exhaled Beta hydrxybutyrate and acetacetate are transprted via the bld t peripheral tissues Use f ketnes generates lts f energy (apprximately 24 ATP) Liver is unable t use ketnes because it lacks the enzyme Succinyl CA transferase Liver just spent time making ketne bdies t exprt having an enzyme t break them dwn wuld be pintless. RBCs dn t use ketnes because they dn t have mitchndria. Main Users: heart, muscle, brain (brain during starving)

8 FA Synthesis After a high carb meal we take C frm the sugar and use it t create FA FA synthesis ccurs in cytplasm f hepatcytes Ingredients in FA synthesis High acetyl C-A (derived frm cytslic citrate!) High NADPH (frm hexse mnphsphate shunt) High CO 2 High ATP 4 Key Enzymes: ACC (Acetyl-CA carbxylase requires ABC) ---- HIGHLY REGULATED ATP Citrate Lyase Glucse 6P Dehydrgenase (NADPH frm HMP and cytslic cnversin f malate) Fatty Acid Synthase Dimer made up f 7 enzymes After a high carb meal High levels f NADH and ATP inhibit iscitrate dehydrgenase B100 retained with vdld What happens t OAA? OAA is reduced t malate by malate dehydrgenase. Malate is then decarbxylated t pyruvate via malic enzyme. This reactin generates NADPH + CO 2 Pyruvate can then be used again t prduce acetyl-ca - Additinal surce f NADPH in additin t HMP LPL is extracellular but it stays in place, it is nly expressed in cells that recgnize tg, its extracell n breaks vdld Lpl held t wall by heperan sulfate (leash) needs apprtein a. cll t activate Rising levels f acetyl-ca inhibit pyruvate dehydrgenase (s n mre cnversin f acetyl CA pyruvate) b. Pyruvate that has built up is diverted and carbxylated t OAA c. OAA cmbines with high levels f acetyl ca citrate in the mitchndria 2. Inhibitin f iscitrate DH causes a build up f citrate in the mitchndria

9 3. Citrate shuttle exprts citrate int the cytplasm where it is split int OAA & acetyl CA via ATP Citrate Lyase 4. Nw we have cytslic acetyl-ca (see what happens t OAA abve) 5. Acetyl ca is nw carbxylated by Acetyl CA Carbxylase (Requires ABC) t frm malnyl-ca (3C) a. Malnyl-cA inhibits CPT-I (used fr FA degradatin ) 6. FA synthase essentially takes acetyl-ca+ malnyl CA yields a 4 carbn mlecule ( adds 2 carbns each time t the starting prduct s if we were building a 16 C FA we wuld have t g thrugh the cycle f FA synthase 7 times ttal) 7. After 16C FA has been created there is a terminatin step in which palmityl thiesterase cleaves the thiester bnd releasing a fully saturated mlecule f palmitate Nw we need t learn a little mre abut ACC and Fatty Acid Synthase Acetyl-CA Carbxylase Highly Regulated Inc Insulin incr acc and fa synthesis and glycgen synth Dimer These are allsteric regulatrs inhibitr n activatr Genetic/Hrmnal High Carb insulin a genetic level insulin activates a phsphatase Dephsphrylated ACC= active Glucagn inhibits ACC (why wuld we want t use energy t make FA if ur energy levels are already lw?) Glucagn activates camp AMPK (lw energy AMP-kinase) Allsteric Regulatin Citrate in the cytplasm turns n ACC -- > causes single subunits t cme tgether t frm dimer Increase in palmityl ca (end prduct f FA synthesis) causes inactivatin f ACC Prlnged cnsumptin f a diet with excess calries cause an increase in ACC synthesis therefre an increase in FA synthesis FA Synthase 4 steps ( Add malnylca+ decarbylate, reduce, dehydrate, reduce) Made up f 7 enzymes Dmain w/ cvalently bund phsph pantetheine (Vitamin B 5 WE DON T MAKE B5 ) Phsph pantetheine is bund t serine residue n acyl carrier prtein (ACP) Acetyl grup is transferred frm acetyl CA t the SH grup f the ACP 2 C fragment is then transferred t a temprary hlding site thil f cysteine The transfer f the 2C fragment t the thil leaves ACP vacant again, s nw ACP picks up malnyl ca (3c) Yu give c2 when malnly c bnds s its 4 c Acetyl grup frm the thil is cndensed with malnyl ca n ACP ( decarbxylatin reactin ) End result: 4 C mlecule still attached t ACP Ket grup is reduced t an alchl via NADPH Dehydratin reactin : H 2 O is remved creating a duble bnd between C 2 and C 3 Duble bnd is reduced via NADPH This prcess is repeated 6x mre t yield a 16C fatty acid Always have additin f 2 Carbns and 2 reductins Once palmitate has been made it can nw be separated frm the ACP via a cleavage by thiesterase Grwing acyl chain must always be held by thiester bnd!!! IT S NOT ALLOWED TO FLOAT AROUND Elngatin & Desaturatin f FA Elngatin Occurs in the SER " cnt affrd synthesis nw "

10 Carbn surce is still malnyl ca Except add mallnly t the grwin acyl c bnd n cash bnd nt acp similar prcess t that f FA synthase Desaturatin Occurs in the SER Requires NADPH, O 2 and Cytchrme b 5 & a FAD linked reductase N desaturase can put a duble bnd after C9 in humans which explains why Linleic acid and linlenic acid are ESSENTIAL Linleic precursr t arachadnic acid (Duble bnd at C9 & C12) (18:2) Linlenic duble bnds at C9, C12, C15 (18:3) Limit dextrase? Nw we have a FA that can either be stred (TAGs) Nt ptentially hful yet In lyssme

11 Glycsaminglycans (GAGs) GAGs are large and negatively charged (they are prteglycans) Cmpsitin: 95% carbs and a small prtein cre (Sugar held t prtein cvalently by O linked except hyalurnate) lng sugar chains Functin: Ability t bind large amunts f water Prduce gel like matrix ECM (GAGs+ ther prteins) Acts as a mlecular sieve (influencing flw f materials thru ECM) Space filler, shck absrber Play a large rle in maintaining vlume Viscus prperty f mucus results frm presence f GAGs Hence the name mucplysaccharides Fund in slutin --- extracellular linear crrelatin between negative charge & shck absrber ability Repel each ther and are surrunded by shells f water mlecules Cmpressed: Water is squeezed ut and GAGs are frced t ccupy a smaller vlume Relaxed: GAGs spring back t nrmal hydrated vlume because f the repulsin f negative charges Structure: Lng, un branched, heterplysaccharide chains cmpsed f a repeating disaccharide unit [acidic sugar-amin sugar] n Amin sugar - D glucsamine r D galactsaine (amin grup is acetylated therefre n + charge) Can be sulfated n C4 r C6 r n a NONacetylated nitrgen Synthesized frm glucsamine 6P (which cmes frm F6-P & Glutamine ) Central sugar remains unchanged Acidic sugar: D-glucurnic acid r L-idurnic acid Carbxyl grps are negeative at physilgic ph ---Sulfate (amin sugar) + carbxyl (acidic sugar) = very LARGE NEGATIVE charge--- Exceptin: Keratin sulfate cntains a galactse instead f an acidic sugar [galactse- amin sugar] n Classificatin Chndritin 4 & 6- Sulfates Extracellular Keratin Sulfates I&II Extracellular Hyalurnic Acid Extracellular Dermatan Sulfate Extracellular Disaccharide Unit N-acetylgalactsamine with sulfate n either C4 r C6 and glucurnic acid N-acetylglucsamine and galactse (n urnic acid) Variable sulfate cntent may be present n C6 f either sugar Mst abundant in bdy Cartilage, tendns, ligaments, arta Frm prteglycan aggregates (nncvalently w/ hyalurnic acid) In cartilage, bind cllagen and hld fibers in a tight, strng netwrk Mst hetergenus GAGs b/c they cntain additinal mnsac. (L-fucse, mannse) KS I- Crnea KS II- LCT N-acetylglucsamine and glucurnic acid Unsulfated Nt cvalently attached t a prtein Fund in bacteria as well Lubricant/Shck absrber Synvial fluid, vitreus humr, umbilical crd, LCT, cartilage N-acetyl galact samine & L-idurnic acid Skin, bld vessels, heart valves Binds LDL t plasma walls Heparin Glucsamine and glucurnic r idurnic acid Alpha linkages jin sugars -Sulfate fund n C3 r C6 f glucsamine & C2 f INTRACELLULAR cmpnent f mast Intracellular urnic acid (apprximately 2.5 per disaccharide cells unit) Anti-cag Causes release f lipprtein lipase frm capillary walls Heparin Sulfate Same as heparin but fewer sulfate grups Basement membrane and cell surface

12 Extracellular Tethers many plasma enzymes t capillary walls - LDL Main chlesterl carrier Synthesis f GAGs Elngated by sequential additin f alternating acidic and amin sugars dnated by their uridine diphsphate derivatives (UDP) Glucse metablism supplies all CH2O cmpnents (inhibitin f PFK1 is necessary t divert F6P) Glucse G6P G1P UDP-glucse UDP galactse, glycgen, prteglycans, glycprteins, glyclipids, OR UDP glucurnate UDP Glucurnate Bilirubin, glucrnides, UDP xylse (GAGs), Idurnate (GAGs), r prteglycans/glycprteins Glucurnate raises slubility and adds negative charge (-COOH). Adds it t things f exgenus rigin enhances eliminatin Reactin is catalyzed by specific glycsyltransferases (frms a glycsidic bnd) Glucsyltransferase glycgen synthase Galactsyltransferase lactse synthase Synthesis ccurs in the Glgi (Because they are exprted frm the cell) -Nnenzymatic sugar attachment is GLYCATION Synthesis f Cre Prtein: Occurs in rer via ribsmes, prtein is then glycsylated by membrane bund glycsyltransferases lcated in the Glgi Synthesis f Amin Sugars N acetylglucsamine & Nacetyl galactsamine F6P is precursr (frm glucsamine 6-P) OH replaced by amin frm glutamine (Attached t C2) Amin grup is acetylated (Acetyl ca) Chemical mdificatin Central sugar - UNCHANGED UDP derivative: GlcNAc & GalNAc N acetylneuraminic acid (NANA) 9 Carbn, acidic Member f sialic acid family F6P is precursr (frm glucsamine 6-P) C & N are frm N-acetylmannsamine & PEP (3 C s) Activated via reactin with CTP CMP NANA synthetase catalyzes rxn ONLY nucletide sugar in human metablism which is activated by a MONOphsphate Side chains (terminus) f glycprteins, glyclipids, r GAGs Synthesis f Acidic Sugars Glucurnic Acid Obtained in small amunts frm diet, lyssmal degradatin f GAGs, G6P via urnic acid pathway UDP glucurnic acid activated frm f glucurnic acid that dnates the sugar in GAG synthesis prduced via xidatin f UDP glucse L-idurnic acid synthesis Occurs after D glucurnic acid has been incrprated int the carbhydrate chain Urnsyl 5 epimerase causes epimerizatin f the D t the L sugar Synthesis f Carbhydrate Chain Shrt linkage regin n the cre prtein Transfer f Xylse frm UDP xylse t the hydrxyl grup f a serine/threnine 2 galactse mlecules are added t the Xylse Cmplete trihexside has frmed Additinal acidic and amin acids are added ne at a time (alternating) via UDP activated sugars Additin f Sulfate Grup Sulfatin ccurs after mnsaccharide has been incrprated int chain Rxn is catalyzed by sulftransferases (attach SO 4 frm PAPS) PAPS-- mlecule f adensine mnphsphate with a sulfate attached t 5 phsphate (AMP+ATP PAPS + ADP) Cst f 1 PAP 3 ATP equivalent

13 **Chndrdystrphies Result frm a defect in sulfatin f grwing chains. Autsmal Recessive. Affects the prper develpment and maintenance f skeletal system. ** Degradatin f Glycsaminglycans (GAGs) Degraded in lyssmes via acid hydrlases (ph 5 prtective s enzymes aren t active if they leak) Enzymes must cntain M6P tag t be claimed by the lyssme Phagcytsis f extracellular Glycsaminglycans GAGs are extracellular and therefre must first be engulfed int a cell Invaginatin f the cell membrane frms a vesicle cntaining GAGs Vesicle fuses with lyssme Next Step: Lyssmal Degradatin Plysaccharide chains are cleaved by end glycsidases prducing ligsaccharides Then ne sugar at a time is remved frm the nn reducing end f ligsaccharides via sulfatases r ex glycsidases Sulfate is the first remved because it was the last ne put n Mucplysaccharidses Characterized by lyssmal accumulatin f GAGs and prevent nrmal cell/tissue remdeling All are autsmal recessive Except: Hunter s Syndrme X linked Nrmal at birth but then prgressively get wrse die in childhd Enzyme deficiencies f ex-glycsidases find inclusin bdies in lyssmes Enzyme deficienc y Features Hurler (MPS I) Autsmal Recessive Hunter (MPS II) X linked Sanfillip Syndrme Autsmal Recessive SLY Syndrme α L-idurnidase Idurnate Sulfatase Defective in 4 steps β-glucurnidase Crneal Cluding Mental Retardatin Carse facial features Mst Severe Degradatin f dermatan sulfate & heparin sulfate is affected Depsitin int crnary arteries leds t ischemia Enzyme replacement available/bne marrw treatment N crneal cluding Variable mental retardatin Wide range f severity Carse facial features Degradatin f dermatan sulfate & heparin sulfate is affected Organ and skeletal defrmities Replacement therapy pssible Severe CNS disrders e arly death Deficiency Type A: heparin sulfamidase Type B: N-acetylglucsaminid ase Type C: glucsaminidie-n-ace tyltransferase Type D: N-acetylglucsamine 6-sulfatase Crneal cluding Hepatsplenmegaly Skeletal defrmity Shrt stature Mental deficiency Degradatin f dermatan sulfate & heparin sulfate is affected

14 Prenatal diagnsis pssible Glycprteins Prteins t which ligsaccharides are cvalently attached Differ frm prteglycans --- length f carbhydrate chain is shrt, n serial repeats, branched, nt always negatively charged, highly variable Functin Cell markers Anitgenicty Receptrs Attachment sites Cmpnents f ECM and f mucins in the GI and UG tract (lubricant) Almst all glbular prteins are glycprteins albumin is an exceptin Structure f Glycprteins (Oligsaccharide) Oligsaccharide may be attached t the prtein via N r O glycsidic link Only ne r the ther Oligsaccharides are D-hexses with additin f neuraminic acid (NANA) O linked: Fund in extracellular glycprteins r as membrane glycprtein cmpunds Abundant H bnding, NANA, negative charges N linked: Branched glycprtein High mannse cntent Synthesis f Glycprteins 1. Mst cytslic prteins are synthesized n free ribsmes 2. Prteins destined fr cell membranes r ther rganelles (lyssmes) are synthesized by ribsmes n the rer a. Then these prteins are sent t the Glgi (srts and tags) 3. Precursr f carbhydrate cmpnents are nucletide sugars all f which release energy when attached a. UPD-glucse b. UDP-galactse c. UDP-GlcNAc d. etc 4. Synthesis f O linked a. Prtein is synthesized in rer and extruded int the lumen b. Glycsylatin begins with the transfer f GalNAc nt the R grup f a specific serine/threnine. i. Glycsyltransferases add sugars ne at a time in the Glgi 5. Synthesis f N linked --bush a. Prtein synthesized in rer & sugars are added in rer b. Require dlichl PP (CH2O bush ) i. A lipid f the ER membrane ii. Lipid linked ligsaccharide cntains N-GlcNAc, mannse, and glucse c. After dlichl is synthesized the whle 14 sugar ligsaccharide is then transferred frm the dlichl t the amide nitrgen f the Asp by a prtein-ligsaccharide transferase

15 Final Prcessing f N-linked ligsaccharide N linked sugars are mdified as they mve thrugh the rer and the final mdificatins ccur in the Glgi Ie. Remval f specific mannse/glucse etc in rer Additin f variety f sugars terminus) in the Glgi Fucse: N OH n C6 Glycprteins: Enzymes destined fr Lyssmes N linked glycprteins being prcessed in the Glgi can acquire a M6P tag N M6P Tag= N enzymes in lyssme Glyclipids Derivative f 18C unsaturated amin alchl Sphingsine Serine cnnected t a fatty acid Ceramide Sphingsine + Fatty Acyl CA Strng & lng lipid like structure permits stable hydrphbic ldging in membrane Cerebrside Single sugar linked t ceramide (ne sugar, ne serine, 2 fatty acyls) Gangliside Glyclipid cntaining N-acetylneuraminic acid (NANA) G M 2 gangliside mn sialic acid grup G D 2 - gangliside with di - sialic acid grup Galactcerebrside Ceramide + Galactse Sphingmyelin CDP-Chline + Ceramide Nt a glyclipid because it desn t have a sugar Chline, phsphate, ceramide Sulfatides Synthesized frm cerebrsides and activated PAPS Glycsphinglipids Sugar attached t hydrxymethyl grup at the tp Glbsides Cerebrsides with additinal carbs (galactse, glucse, GalNAc) ABO Bld type Glyclipids make up the antigenic termini n A &B O cntains n antigenic terminus R grups is either a prtein r ceramide that is embedded in the membrane Glyclipid Synthesis Ceramide is created by sphingsine amide link t a FA Glgi synthesizes in a similar fashin t GAGs (assemble prtein then add ne sugar at a time) Glyclipid Degradatin Degraded by lyssmes Defect in lyssmal degradatin causes sphinglipidses- deficiencies are specific t ne enzyme s cmpsitin f inclusin bdies are dependent n which enzyme is defective Disease Enzyme Type f Glyclipid that Accumulates Gaucher s Disease Beta glucsidase Gluccerebrsides

16 Metachrmic Leukdystrphy Arylsulfatase A Sulfatides Niemann Pick Disease Sphingmyelinase Sphingmyelin Farber Disease Ceramidase Sphingsine Tay- Sach s disease Hexaminidase A GM2 Gangliside Fabry Disease Alpha galactsidase Glbsides Phsphlipid & Glyclipid Metablism 1. All phsphlipids cntain a hydrphilic head and 2 lng hydrphbic tails 1. Head- has a negative charge cntaining a phsphate grup (smetimes a sugar) 2. Tail- anchrs it t the membrane 2. Cmpsed f an alchl attached by a phsphdiester bridge t either DAG r SP 1. DAG - diacylglycerl glycerl with tw fatty acids 2. SP sphingmyelin sle PL with n glycerl platfrm (Fatty acid, Phsphcline, ceramide) 3. Universal, repeated, design features implies that they have glbal functins 4. Glycerl 3P is the precursr t phsphlipids 1. Glycerl 3P cmes frm DHAP r glycerl 1. DHAP--- Glycerl 3 Phsphate dehydrgenase +NADH Glycerl 3 P (adipse+liver) 2. Glycerl--- Glycerl Kinase +ATP Glycerl 3P (liver ONLY) Assembly f Phsphlipids 1. Synthesis: ser 2. Transprted t Glgi 3. Shipped t destinatin (plasma membrane r ther rganelles) r packaged in vesicles fr excytsis Functin 4. Membrane architecture 5. Surce f intracellular messengers (2 nd & 3 rd ) 6. Membrane prtein anchrs 7. Nn-membrane bund phsphlipids can act as detergents, bile cmpnents, lung surfactant General Structure 3 Types f Phsphlipids Glycerphsphlipids - majr cmpnents f cellular membrane, lipprteins,bile and surfactant Glycerl backbne FA at C1 & C2 f glycerl are jined by an ester bnd Head grup (chline, serine, insitl, etc) is attached via a phsphate at C3 Examples include: Phsphatidyl chline Phsphatidyl ethanlamine Phsphatidyli nsitl Phsphatidyl serine Cardilipin Phsphatidylglycerl Ether glycerlipids Glycerl backbne Examples include Plasmalgens C1 f glycerl is jined by an ether linkage t a lng chain hydrcarbn with an unsaturated tail Head is usually chline r ethanlamine

17 Platelet activating factr C1 is linked t a saturated alkyl grup via an ether bnd C2 f the glycerl backbne is attached t acetyl residue via an ether linkage Sphingphsphlipids Sphingsine backbne NO glycerl Sphingmyelin is the nly type f sphingphsphlipid Phsphcline & ceramide (sphingsine w/ an amide linked FA) Als cnsidered a sphinglipid Sphinglipids n uter leaflet f membrane and bld grup determinants Glycsylated Sphinglipids sugars via glycsidic bnds glycsphinglipids Synthesis f Glycerl 3 Phsphate 1. Can either cme frm DHAP r Glycerl 2. DHAP is cnverted t Glycerl 3p via Glycerl 3P Dehydrgenase (Liver and mst ther tissues) 3. Glycerl can be phsphrylated directly t Glycerl 3 Phsphate by glycerl kinase nly fund in the liver Synthesis f Phsphatidic Acid 1. Glycerl 3 Phsphate and add 1 FA via an acyl transferase (Happens 2x 3+2= 5C) 1. 2 ATP were used t activate each fatty acid 2. Activatin f Phsphatidic Acid 1. Phsphatidic Acid + CTP CDP+DAG (ACTIVE NOW!) 2. CDP-bund structure is the activated intermediate CDP+ head grup 3. CTP prvides activating grup CDP (CDP= Cytidine diphsphate= activating head grup!) 4. CMP is released after CDP has been bund 5. Phsphatidic Acid is a precursr t many ther cmpunds 6. Phsphatidylethanamine, phsphatidylserine, phsphatidychline are all frmed frm DAG just with different head grup (requires CDP t be bund t head grup )

18 Phsphatidylchline (PC) and Phsphatidylethanlamine (PE) Synthesis PC & PE are the mst abundant phsphlipids in mst eukarytic cell Chline and ethanlamine can be btained either frm the diet r frm the turnver f the bdy s phsphlipids Synthesis frm pre-existing chline and ethanlamine Synthetic pathways invlve the phsphrylatin f chline r ethanlamine by kinases After being phsphrylated Cnverted t activated frm (CDP-chline) Chline-phsphate is transferred frm the nucletide t a mlecule f DAG Releasing CMP S-adensyl methinine dnates a methyl grup t phsphatidychline frm phsphatidylethanlamine (3 SAM required t g frm PE PC) SAM is created by a cmbinatin f methinine + ATP release f PPPi and creatin f SAM SAM dnatin f CH 3 t PC creates S-adensylhmcysteine (SAH) SAH can nw re-enter methinine/cysteine metablism De nv synthesis f chline is insufficient fr ur needs therefre chline is an essential dietary nutrient Lung surfactant Di palmityl - phsphatidychline ( DPPC ) is made in the ER and secreted by Type II pneumcytes Majr cmpnent f lung surfactant Reduces surface tensin Activated after birth and acceleratin f synthesis is crucial at 35 weeks. Synthesis is activated by translcatin frm cytsl t ER f CTP -phsphchline cytidyl transferase Hyaline Membrane Disease/Respiratry Distress Syndrme : insufficient surfactant prductin. Often ccurs in nenates f diabetic mthers r in premature infants because enzyme isn t fully active until 35 weeks. Lung maturity f the fetus can be gauged by determining the rati f DPPC t sphingmyelin in amnitic fluid. A value f 2 + reflects the majr shift frm sphingmyelin t DPPC synthesis that ccurs in pneumcytes at 32 weeks f age Phsphatidylinsitl(PI) Synthesized frm free insitl and CDP-DAG Serves as a reservir fr arachidnic acid in membranes and prvides a substrate fr prstaglandin synthesis when required. Phsphrylatin f membrane bund PI PIP2 Cleavage f PIP 2 by PLC IP 3 and DAG (Respnse t binding f NT, hrmnes, and grwth factrs t G prtein cupled receptrs) PLC Cuts at C1 DAG and IP 3 (2 nd messengers ) mediate mbilizatin f intracellular calcium and activate PKC Als acts as a membrane anchr Cardilipin 1. CDP DAG + Phsphatidylglycerl Cardilipin

19 2. Phsphatidylglycerl fund in large amunts in the mitchndrial membranes and is a precursr f cardilipin 3. Strng acid, that is fuld exclusively n the inner mitchndrial membrane in eukarytes and helps t stabilize the mitchndrial membrane Plasmalgen Ether Glycerlipids 1. Unsaturated alkyl C1 with vinyl ether link 2. FA is exchanged fr the fatty alchl MAKES PLASMALOGEN A VERY STABLE ETHER 3. Synthesis f plasmalgens takes place in the perxismes 4. Perxismes break dwn txic substances, synthesize lipids and are required in all tissues 1. Defective perxismal synthesis Zellweger s Syndrme 1. Mutatin in genes that cde fr perxins 2. Results frm dysfunctinal lipid metablism, ver accumulatin f VLCFA, phytanic acid, defects f bile acids and plasmlgens 3. Characteristics: Enlarged liver, underdevelped eyebrw ridges, wide-set eyes, hyptnia. 4. Plasmalgen defects= death 5. Invlved in many vital tissues/ 1. Heart (50%) 2. Brain 3. Muscle 4. Myelin Sheath!!! (70%) Platelet Activating Factr (PAF) is a Plasmalgen 1. Ether gylcerphsphlipid 2. Has a SATURATED FA at C1 and an acetyl grup at C2 3. Used in hst defenses 1. Helps lwer BP 2. Triggers 1. Platelet aggregatin and cltting 2. Macrphages t make ROS 3. Inflammatin Degradatin f Phsphlipids 1. Phsphlipases (PLs) are fund in all tissues, venm, pancreatic juices etc. 1. Used t disslve the membrane f the hst Lcatin Phsphlipase A 2 Mammalian Tissue Pancreatic Juice Phsphlipase C Liver Lyssmes alpha txin f clstridia and ther bacilli Functin Acts n PI and releases arachidnic acid In the pancreas it is released as a prenzyme and then is activated by trypsin and requires bile salts fr it s activity Requires Ca+2 fr activity Inhibited by gluccrticids Membrane bund PLC is activated by PIP 2 system and therefre plays a rle in prductin f secnd messengers

20 Phsphlipase D Plant Tissue Arachidnic acid (20C) precursr fr an eicsanid FA Sphinglipids Sphingsine backbne 18 C unsaturated amin alchl Sphingmyelin sle PL withut Gylcerl Cntains phphchline Ceramide + Phsphatidylchline= sphingmyelin Sphingmyelinase degrades sphingmyelin in the lyssmes Wrks best at a lw ph Releases p-chline and ceramide Eicsanids Prstaglandins, leuktrienes and thrmbxanes are cllectively knwn as the eicsanids Reflect their rigin frm a 20 C plyunsaturated (4 duble bnd) FA (arachidnic acid ) Extremely ptent cmpuds and elicit a wide range f respnses Act lcally and have an extremely shrt half life (rapidly metablized t inactive prducts) Act in all tissues EXCEPT lymphcytes and RBCs Ensure gastric integrity, renal functin, bld vessel diameter, platelet hmestasis Synthesis f Eicsanids- NO De Nv Requires Linleic Acid (18:2) Arachidnic acid ω -6 fatty acid : 20 Carbns & 4 duble bnds immediate precursr f prstaglandins Derived frm elngatin and desaturatin f linleic acid (essential fatty acid) Incrprated int INNER leaflet membrane phsphlipids (PI ) at C2 (via esterificatin) Released by via PLA 2 r PLC Binding f a stimulus (cytkines, histamine etc) t a membrane receptr activates pathway 1 (Phsphlipase A 2 ) r 2 (Phsphlipase C) Pathway 1- Rapid Respnse Pathway 2 Enzyme Phsphlipase A 2 (Ca+2 required) Phsphlipase C Reactants Phsphatidyl-chline Phsphatidyl insitl Mechanis m Breaks ester bnd at C2 Phsphlipid remains w/n membrane Breaks ff phsphr-insitl frm C1 & C3 Leaves DAG with arachidnate still at C2 Aracihidnate is liberated by DAG Lipase -Invlves destructin f the phsphlipid cmplex frm the membrane decreasing membrane integrity Prducts Arachidnic acid (1 step) DAG arachidnic acid+ mnacylglycerl Nw that we have Arachidnic Acid Pathway activity varies with tissue functin Mnacylglycerl arachidnic acid (via a lipase) = 2 mlecules f arachidnic acid -Phsphinsitl is then recycled t recnstitute the riginal phsphatidyl insitl in inner membrane

21 Three pssible pathways Cycl-xygenase (COX) prductin f prstaglandin, prstacyclin and thrmbxanes Lipxygenase leuktrienes, HETES, lipxins Cytchrme P450 epixides, HETEs, di HETEs HETE H ydrxy- Ei csa- T etra- E nic Aci Prducts: Prstaglandins 20 C FA; 5 sided ring Prstacyclin 20 C FA: w/ 2, 5 sided rings Cycl-xygenase (COX) Pathway PGI 2 Prduced by vascular endthelial cells INHIBITS platelet aggregatin Causes vas dilatin Thrmbxanes 6 sided ring with central O Thrmbxane A 2 is created by cnstitutive COX1 and inducible COX2 TXA 2 Functins are all hemstatic Prduced by platelets STIMULATES platelet aggregatin BLOOD CLOTTING Causes vas cnstrictin Lymphcyte prliferatin Brnch cnstrictin Mbilizes intracellular Ca+2 Arachidnate PGG 2 via COX and 2O 2 PGG 2 -->PGH 2 via Perxidases (Uses Gluthatine frm HMP fr reducing pwer) PGH 2 is cnverted int its respective prducts by a tissue specific synthase Ex/ TXA 2 is prduced via TXA synthase COX 1 COX 2 Type Cnstitutive- lw levels Inducible by allergic rxns Lcatin Gastric mucsa, platelets, vascular endthelium, kidney Inductin is suppressed by gluccrticids Activated by macrphages and mncytes

22 Primary Functin Platelet aggregatin & stmach Inflammatry, hyperalgesia cytprtectin Respnse t NSAIDs Decreased activity Decreased activity COX 2 Inhibitr N effect Decreased activity Tw isfrms f COX enzymes bth are hmdimers -NSAIDs nn steridal anti-inflammatry drugs such as aspirin r tyelenl that functin as un cmpetitive inhibitrs f bth COX 1 & 2 Prstaglandins & Thrmbxanes Play a huge rle in inflammatin defense Macrphages and ther prtective cells are lcal mediatrs f inflammatin Histamine, leuktrienes and assrted WBC cytkines Inflammatin Damaged cells, mast cells and basphils release histamine Redness, heat, thrugh vasdilatin Swelling frm engrgement f tissue with plasma and phagcytes attracted by leuktriene derived chemical signals (chemkines) Phagcytes prduce cytkines affect thermregulatry center prduce fever In extreme inflammatin COX inhibitrs can be administered Sterids NSAIDS (aspirin, Tylenl, ibuprfen) Lipxygenase Pathway 5 lipxygenase Prducts are Leuktriene Synthesized in leukcytes triene 3 duble bnds in a rw Relatively stable persist fr hurs Brnchial and intestinal smth muscle LTC 4, LTD 4, LTE 4 are all implicated in brnch-cnstrictin (asthma) Slw Reacting Substance f Anaphylaxis (SRS-A) is a LT Can lead t anaphylactic reactin and is x mre ptent then histamine Hydrxyeicsatetraenic (HETE) Present in high amunts in cular, vascular, renal and endcrine (anywhere bld supply is rich) Mediate big allergic and inflammatin respnses Lipxin Induce chemtaxis and stimulate O 2 uptake in leukcytes Lipxygenase is NOT inhibited by NSAIDs Lipxygenase inhibitrs are fund in Asthma treatment Excessive Inflammatin Tw drugs can blck synthesis f eicsanids (SAIDs & NSAIDs) SAIDs Gluccrticids blcks PLA 2 (typically the rate limiting step). S if PLA 2 is blcked, all prductin f eicsanids is blcked and COX 2 synthesis NSAIDs Uncmpetitive inhibitin at varius steps by interacting with the hydrxyl f serine in the active site Des nt blck active site, but prevents arachidnate frm binding with serine Uncmpetitive inhibitin: cvalent adduct n bth COX1 and COX2 Aspirin - permanent inhibitr Lw dse aspirin is effective at blcking TXA 2 withut affecting PGI 2

23 If it were t affect PGI2 yu wuld end up with vascnstrictin Tylenl and Ibuprfen nt permanent inhibitrs Acts n synthesis f eicsanids Aspirin is nt given t patients with asthma Brnch-cnstrictin is induced by leukrtrines rather than prstaglandins Aspirin inhibits COX and NOT lipxygenase then arachidnate metablism is shifted t leuktriene synthesis-- > causes mre vascnstrictin Chlesterl Can be btained frm diet and synthesized de nv via the liver and extra hepatic cells (as lng as they have HMG-CA reductase and an ER ) RBCs cannt prduce chlesterl (NO ER) Balance between intake and efflux is NOT precise s yu end up with chlesterl depsited n tissues Can lead t issues plaque frmatin etc. Free chlesterl is mst abundant in membranes and membrane rich tissue RBC & bne marrw Esterified chlesterl is used fr strage Functins Structural cmpnent f all cell membranes mdulating their fluidity (increases rigidity) Precursr f bile acids, sterids, and vitamin D Structure f Chlesterl Very hydrphbic (Chlesterl esters are 100% hydrphbic) very lw slubility Inflexible 4 fused hydrcarbn rings aka sterid nucleus indestructible Majr sterl in animal tissues Sterl 8-10 C in the side chain at C17 & OH at C3 Mst plasma chlesterl is present in an esterified frm (FA attached at C3) Esterificatin makes chlesterl even MORE hydrphbic Nt fund in membranes Transprted in cnjunctin with a prtein r is sled by phsphlipids and bile salts in bile Synthesis f Chlesterl - Absrptin f chlesterl is extremely efficient because it s very expensive t make! All carbn atms cme frm cytslic acetyl CA (shuttled ut via citrate) NADPH is required fr reductins Endergnic pathway and is driven by the exergnic hydrlysis f PPi Requires enzymes in the cytsl and the ER Pathway is respnsive t changes in levels f chlesterl Liver has tw isfrms f HMG CA synthase Mitchndrial: ketne bdy synthesis

24 Cytslic: chlesterl synthesis -Chlesterl is always essential fr sterids, bile salts, and membranes s efficient absrptin is beneficial Synthesis f Chlesterl (cntinued) Prcess is repetitive and hugely EXERGONIC (hydrlysis f PPi) The cyclizatin f squalene lansterl requires the enzyme Squalene mngxygenase Squalene mngyxgenase Cytchrme P450 family member, and requires NADPH Cytchrme P450 enzymes require xygen bund t a heme grup Regulatin f Chlesterl Synthesis HMG CA reductase is the majr regulatry enzyme f chlesterl synthesis and is subject t multiple types f cntrl Transcriptinal Sterl Regulatry Element Binding Prtein(SREB)- mediated hrmnally Increase transcriptin with high insulin Decrease transcriptin with high glucagn SREB binds with cleavage activating prtein fund in the ER membrane t frm a cmplex SREB-SCAP Lw sterl levels : SREBP-SCAP mves frm ER t the Glgi cleaved by prteases leaves a sluble fragment that is able t translcate int the nucleus and binds t SRE therefre functining as a TF and inducing transcriptin f HMG CA reductase increasing chlesterl synthesis High levels f chlesterl : Sterl binds t SCAP at a particular dmain and induces SCAP t bind t insigs (insulin dependent prducts) and retentin f SREBP-SCAP cmplex prevents activatin f SREPB Degradatin: Very shrt half life at high sterl levels (a little lnger at lw levels f chlesterl) HMG CA is a sterl sensing integral prtein f the ER membrane. High sterl levels: Enzyme binds t insig prteins, which leads t a ubiquitin-prteasmal degradatin f the reductase. Ubiquitin is cnjugated t a specific lysine residue in HMG-CA Ubiquinated-HMG CA is extracted frm membrane by an ATPase delivered t a prteasme fr degradatin. Pathway is nt stimulated by chlesterl itself Cvalent Mdificatin: HMG CA reductase activity is als cntrlled via phsphrylatin Insulin is present after a high carb meal. Insulin indirectly activates a phsphatase and the de-phsphrylatin activates HMG-CA Glucagn is present at lw energy levels and activates AMPK (which is stimulated by AMP), which phsphrylates the enzyme rendering it inactive. Allsteric: High chlesterl levels: Inhibits enzyme Lw chlesterl levels: Activates enzyme Chlesterl derivatives in plants Squalene has a number f cnjugated duble bnds Squalene can NOT be cyclized int lansterl in plants Instead, a desaturatin ccurs t create a stiff mlecule that cannt cyclize t create phytenes, lycpenes, and beta cartene Plants DON T prduce chlesterl ( veggie diet= chlesterl free)

25 These cmpunds have many cnjugated duble bnds and are therefre able t absrb almst all wave lengths red tmates, range carrts etc. Ptent antixidants strngly absrb/detxify ROS (Lycpene!) Statins Cmpetitive Inhibitrs f HMG CA reductase thereby blcking chlesterl synthesis Km increases, Vmax stays the same Functinal grup f statin drugs mimics HMG CA Lwer chlesterl synthesis can be used t manage hyperchlesterlemia Increases prductin f LDL receptrs Fate f Chlesterl Mst hepatic chlesterl leaves the liver as chlesterl esters, biliary chlesterl, and bile salts. Esterified chlesterl Free chlesterl is cnverted t an esterified versin fr strage via Acyl-CA-chlesterl acyl Transferase 100% hydrphbic mst efficient strage frm Bile Salt Synthesis Synthesized in the liver Inized frm is the salt pka f 6.0 (COOH) Hydrxyls α rientatin & methyl grups in β Mlecules are plar and nnplar and can act as emulsifying agents Variable in cmpsitin Chlesterl, bile acids, lecithin, and heme derived pigments Rate limiting step in Bile Synthesis 7 α hydrxylase ER assciated Cytchrme P450 mnxygenase ONLY fund in the liver Requires NADPH & Vitamin C Expressin f the enzyme is dwnregulated by levels f bile acids High bile salt/acid levels decrease in enzyme activity High chlesterl increases activity Regulatin f enzyme is interlcked with HMG-CA reductase regulatin

26 Synthesis f Cnjugated Bile Acids Befre leaving the liver, bile acids are cnjugated t a mlecule f either glycine r taurine Reactin requires ATP (ATP AMP+PPi) Acetyl CA is required t activate chlic acid Rati f Glycchlate ( Glycine) : Taurchlate ( Taurine ) in bile is 3:1 (reflects really lw pka) Glycchlic acid- pka f 4 Taurchlic acid= pka f 2 Inized bile salts are mre effective detergents than the uncnjugated nes Only CONJUGATED is fund in bile Enterhepatic Circulatin Bacteria in the intestine can decnjugate (remve taurine and glycine) and remve the hydrxyl grup at C7 prducing secndary neutral bile secndary bile salts Bile secreted int the intestine are efficiently reabsrbed (greater than 95%) and resused. Secreted liver Absrbed terminal ileum via a Na+ bile salt c-transprter Absrptin is imprtant because chlesterl is very energetically expensive. S if there is an efficient absrptin bile salts can be recycled instead f made each time. Fate f Chlesterl (Cnt) Precursr t Vitamin D Mst abundant frm is Vitamin D 3 (chlecalciferl) Essential in UV free envirnment n UV= n chlecalciferl Only UV light can pen ring B (N enzyme can pen the ring!) Vitamin D 3 is a prhrmne that acts analgusly t a sterid hrmne nce active Bund by SREBP Functins: Regulate calcium and phsphate metablism in bne. 7-Dehydrchlesterl Chlescaliferl (D 3 ) via UV light Isprenids Derivatives f Mevalnic Acid Plants prduce a lt f them All FAT sluble vitamins - A,D,E,K Phytanic acid (frm alpha xidatin f FA) are isprenids Can accumulate in patients and cause Refsum s disease if patient lacks phytanyl-ca hydrxylase Humans synthesize a limited number f them Ubiquinne - electrn transprt Dlichl -assembly f N linked ligsaccharides f glycprteins

27 Side chain f Heme A - prsthetic grup f Cytchrme A Farnesyl (15) r Geranylgeranyl (20C)- Membrnae prtein anchrs Farnesyl transferase Targets in cancer chemtherapy because inhibitrs can interfere with cell grwth. Exergnically created by the additin f ispentyl-pp units (Each time the PPi is hydrlyzed releasing energy) Sterids Chlesterl is the precursr f all classes f sterid hrmnes Gluccrticids (crtisl) STIMULATE glucnegenesis Sex Hrmnes (andrgens, estrgens, and prgestins) Mineralcrticids (aldsterne) Synthesis and secretin ccur in the Adrenal Crtex (crtisl, aldseterne, and andrgens) Ovaries and placenta (estrgen and prgestin) Testis (teststerne) Transprted frm site f synthesis t target rgans via bld Must be cmplexed with a plasma prtein (b/c they are hydrphbic) Albumin nnspecific plasma carrier carries aldsterne Sterid-carrier plasma prteins bind sterid hrmnes tightly Type f Hrmne Autcrine Paracrine Endcrine Characteristics Messenger acts upn same cell that has synthesized it N transprt via bld Diffuses t neighbring cells/tissues and elicits a lcal respnse Synthesized in ne tissue and transprted t its distant target rgan via bld Key Characteristics abut Sterids Only the side chain can be altered Sterid nucleus (4 rings) ALWAYS stays INTACT Ring can be decrated via xidatin/hydrxylatinr reactins ALL reactins are mediated by Cyt P450 enzymes (all require NADPH and O 2 ) Exceptin: Pregnennlne Prgesterne requires 3-β dehydrgenase requires NAD+ If this step is deficient NO HORMONES! All sterids have either an - OH r an =O attached t C3 f Ring A CYP 21 (21-α-hydrxylase) used in synthesis f aldsterne and gluccrticids 21-α-hydrxylase CAHDeficiency in CYP21 wiill present as

28 Synthesis f Sterid Hrmnes Invlves shrtening f hydrcarbn side chain f chlesterl and hydrxylatin f sterid nucleus Initial and Rate Limiting Reactin Chlesterl mves frm the uter mitchndrial membrane t the inner mitchndrial membrane This translcatin is mediated by StAR (steridgenic acute regulatry prtein) Once chlesterl has mved int the inner mitchndrial membrane it is cnverted int pregnenlne (21 C) Catalyzed by chlesterl side chain cleavage enzyme cmplex (Cytchrme P450) Aka DESMOLASE Fund n the inner mitchndrial membrane Requires NADPH and Mlecular Oxygen Pregnenlne is the parent cmpund fr all sterid hrmnes Armatase causes cyclizatin f Ring A Cytchrme P450 Functin in the additin f hydrxyl grups (Never transferred ONLY created!) Require NADPH & O 2 Cntain a heme cfactr (Fe+2) Fund in either the mitchndria r the ER Cytchrme p450 are induced by xenbitics (freign prducts=barbituates, antifungal, tbacc) Synthesis f Sterids & Diseases (Diagram)

29 Sterids are able t diffuse acrss the plasma membrane f its target cell and bind t a specific cytslic r nuclear receptr ( All Sterid Receptrs are INTRACELLULAR). Hrmne binds t receptr and receptr-hrmne cmplex binds t Hrmne Respnse Element (HRE) n DNA Enhancer Regin. Causes a cnfrmatinal change in the receptr that uncvers a DNA binding dmain allws zinc finger interactin with apprpriate sequence n DNA transcriptin upregulated. Lcatin Hrmne Mechanism Side Ntes

30 Adrenal Crtex Outer Layer Zna Glmerulsa Middle Layer Zna Fasciculata Inner (Zna reticularis) & Middle Layer Gnads Aldsterne Crtisl Andrgen Teststern e Estrgen Induced by a decrease in extracellular Na+ and/r Angitensin II Binding f aldsterne t nuclear membrane receptrs in principle cells f the DT & CD f the nephrn and up-regulates synthesis (activates) Na/K pump Results in reabsrptin f mre Na+ thereby increasing the amunt f fluid reabsrbed Secreted in times f stress. Crtictrpin Releasing Hrmne ( CRH ) released by hypthalamus CRH stimulates prductin f Adren-CrticTrpic Hrmne ( ACTH ) in the anterir pituitary gland ACTH stimulates crtisl prductin in the adrenal crtex Crtisl allws the bdy t respnd t stressful situatins glucnegenesis induced (camp levels rise!) Prduce dehydrepiandrsterne and andrstenedine Estrgens are derived frm andrstenedine and testersterne by armatase (CYP19). Armatase inhibitrs are used in the treatment f estrgen-respnsive breast cancer Majr andrgen frm Leydig cells f the testes Precursr t mre active Dihydrxyeststerne -DHT (see 5 α reductase deficiency previus page) Precursr t estradil & andrstenedine Induced by LH & FSH Synthesized directly frm teststerne Secreted frm Granulsa cells f varian fllicle r placenta (during pregnancy) Induced by LH & FSH Lw Na+/K+ rati can be reflected as a lwer bld vlume/lw bld pressure Angitensin II binds t G prtein cupled receptrs and activates PLC PIP2 IP3 + DAG Na is reabsrbed with Cl t maintain electrlyte balance K is secreted with urine. ACTH = stress hrmne Negative feedback lp in place. As crtisl levels rise, ACTH and CRH are inhibited ACTH binds t G prtein cupled receptr increasing camp PKA activates esterase t free chlesterl Weak until they are cnverted int teststerne in tissues - Andrgens are als prduced in the testis LH stimulates testes receptrs t prduce teststerne FSH stimulates testicular spermatgenesis Small amunts f estrgen are secreted by males via the micrsmal armatase prduce estrgen in adipse tissue, liver, skin, brain LH stimulates the varies t prduce estrgen FSH regulates grwth f varian fllicles Angitensin II prductin Angitensingen secreted by the liver Cleaved by renin (made and secreted by kidney) int active Angitensin I Angitensin II is cnverted by Angitensin Cnverting Enzyme (ACE) int Angitensin II Angitensin II binds t receptr and activates G prtein cupled receptrs PLC PIP2 DAG Prductin f aldsterne! enhanced Na+ uptake and K+ secretin (increase in extracellular Na+) bld pressure increases Hypertensin: ACE inhibitrs can be given t lwer BP

31 Cushing Syndrme: Hypersecretin f ACTH due t an adenma (tumr) f the pituitary gland. Causes an verprductin f crticsterids leading t besity, mn facies, buffal hump large truncal fat depsits, acne, and hirsutism (male pattern hair grwth in wmen) Addisn s Disease: Hyp-crticism ( lack f crtisl ) ften due t an autimmune disease (TB) r a bilateral destructin f the adrenal crtex. Insufficient prductin f bth gluccrticids and mineral crticids hypglycemia, electrlyte imbalance, hyptensin. 1.5x mre likely t ccur in a female. Symptms are nn-specific weight lss, vmiting, anrexia. Lcal hyperpigmentatin (gums). Is ften a diagnstic sign. Death within 1-2 weeks if n replacement therapy available because all critical rgan systems are affected. Death directly caused by circulatry cllapse. Onset in adults. Uses f Anablic/Andrgenic Sterids (AAS) Bne marrw stimulatin increase RBC cunt Grwth stimulatin Bdy mass cnservatin/appetite stimulatin (used in HIV/AIDS and cancer) Used fr hrmne therapy in hypgnadism & gender dysmrpha Causes accelerated bne maturatin in adlescence Sustann, Teststerne-enanthatate Cnsequences Increase chlesterl (Increase LDL, Decrease HDL) High BP Hepatxicity Altered Left Ventricle Mrphlgy Males Testicular atrphy Pr spermatgenesis (Fertility issues) Accelerated baldness, aggressin Females Hirsutism Deeper vice Menstrual cycle disruptin (Fertility issues) Fetal grwth retardatin if pregnant Many prducts can cause sterid effects. Pesticides interact with estrgen receptrs Csmetic Cmpnents endcrine disrupters Dairy estrgen in dairy prducts linked t rapid rises in hrmne related cancers Eliminatin f Sterids Cnverted t inactive metablic excretin prducts in the liver Reductin f unsaturated bnds and intrductin f additinal OH grups After this has been dne glucurnic acid r sulfate make these even mre sluble by cnjugatin Sme are secreted int bile and then excreted int the feces and the rest are secreted via urine DO NOT NEED PROTEIN CARRIERS nce cnjugated.

32 Degradatin f Dietary Lipid Lipids are the primary strage frm f energy because f its hydrphbic nature (if glycgen were used we d weigh t much) Lipids are fund cmpartmentalized Average daily intake f lipids is abut 81 g (90% is nrmally TAG) Remainder is chlesterl, chlesteryl etsters, phsphlipids and free chlesterl Acid stable lipases are used in the stmach s that they stay active in their envirnment Primary value f lw ph is fr prtein denaturatin and t destry any freign antigens/bacteria Prcessing f dietary lipid Digestin f lipids begins in the stmach Catalyzed by lingual lipase that riginates frm glands at the back f the tngue TAGs that are shrt medium chain (fewer than 12 C) are the primary target f this enzyme Degradatin f these lipids ccurs via gastric lipase secreted by the gastric mucsa. Acid stable Emulsificatin f lipids ccurs in the dudenum Emulsificatin increases the surface area f the hydrphbic lipid drplets (micelle ) s that the digestive enzymes can be effective. Digestive enzymes graze the surface and FA are extracted ne at a time. Accmplished by a cmbinatin f mechanical mixing and bile salts (detergent prperties) Bile salts Glycchlic acid/glycchlate & taurchlic acid/taurchlate Degradatin f Dietary enzymes via pancreatic enzymes TAGs, chlesteryl esters, and phsphlipids are degraded by pancreatic enzymes Secretin f fatty acids are under hrmnal cntrl TAG Degradatin TAG mlecules are t large t be taken up by mucsal cells f intestinal villi Acted upn via an esterase and pancreatic lipase which preferentially remves the FA at C1 and C3 Primary prducts are a mixture f 2-MAG and FFA Clipase is anther enzyme that binds lipase at a rati f 1:1 and anchrs it t the lipid-aqueus interface Restres activity f lipase in the presence f inhibitry substances like bile acids that bind the micelles Chlesterl Esters Hydrlyzed by pancreatic chlesterl esterase yu end up with FFA & free chlesterl Free chlesterl degradatin Mst dietary chlesterl is present in the free frm Phsphlipid Degradatin Pancreatic juice is rich in prclipase which is the prenzyme f Phsphlipase A 2 Once in the stmach Prclipase is cleaved by trypsin int Phsphlipase A 2 Phsphlipase A 2 remves 1 FA frm C2 f a phsphlipid lysphsphlipid Lysphsphlipid (aka lyslecithin ) glycerylphsphryl base via lysphsphlipase Glycerylphsphryl base can be excreted in feces r absrbed Cntrl f lipid digestin Pancreatic secretins that degrade lipids are hrmnally cntrlled insulin Chlecystkinin (CCK) Secreted by mucusal cells in the dudenum and jejunum Secreted in respnse t the presence f lipids and partially digested prteins Acts n gallbladder and n the pancreas release f bile and pancreatic digestive enzymes Decreases gastric mtility therefre decreasing gastric emptying Secretin Causes the pancreas and liver t release bicarb neutralizatin Released in respnse t the lw ph in chyme enables pancreatic enzymes t wrk at neutral ph

33 We ve degraded the lipids s nw what? Absrptin f lipids FFA, free chlesterl and 2-MAG are the primary prducts f lipid digestin in the jejunum Fat sluble vitamins (A,D,E,K) and bile salts are als present These ingredients calesce and frm mixed micelles (hydrphbic grups inside & hydrphilic grups utside) Micelles are amphipathic and are sluble (b/c hydrphilic grups are n the utside) Brush brder is the primary site f lipid absrptin Entercytes (mucusal cells f the small intestine) make up this brush brder Fenestrated epithelium Shrt & Medium chain length FA readily enter the entercyte WITHOUT the assistance f a micelle Resynthesisis f TAG and chlesteryl Esters Mixture f lipids migrates t the ER f the entercyte where bisynthesis f cmplex lipids takes place FA Fatty acyl CA via fatty acyl-ca synthetase (thikinase) = activated Requires ATP AMP +PPi & CA Fatty acyl CA + 2-MAG TAG by TAG synthase TAG synthase has functins f 2 different enzymes Chlesterl is re-esterified t a fatty acid via chlesterl acyltransferase Lysphsphlipids phsphlipids In essence everything is recnverted t its initial frm Anything that WAS NOT COVERTED TO THEIR DERIVATIVES Shrt and Medium chain fatty acids that were NOT cnverted t their derivatives (did nt travel in the micelle) enter the prtal circulatin directly and are picked up by albumin and transprted t the liver. Secretin f lipids frm Entercytes Newly synthesized TAGs and chlesteryl esters are very hydrphbic Aggregatin ccurs in an aqueus envirnment Chylmicrns are frmed sle lipid carrier f dietary lipid Packaged particle lipid drplets (chlesterl esters and TAGs n the inside) Outer layer stabilizes the particle and increases slubility decreasing aggregatin Cnsists f: Phsphlipids Unesterified chlesterl Aplipprtein B-48 Unique t chylmicrns. Called 48 because it cnstitutes 48% f the prtein cded fr by the gene fr ap B RNA editing deaminates a C U thus creating a STOP cdn N S-S bridge and is alpha helical in structure Cmpared t ApB-100 which represents the entire prtein cded fr by the ap B gene ( Ap-B-100 is fr VLDL & LDL and is synthesized in the liver ) Micrsmal TAG (MTP) transfer prtein is required fr assembly f chylmicrns in the ER Accelerates transprt f TAG, chlesterl esters and phsphlipid acrss rganelle membrane s they can assemble int chylmicrns. As Ap-B-48 is made lipids are able t cmbine ( reactin is catalyzed by MTP ) this reactin cntinues till chylmicrs are ready t leave the cell. After assembly f the chylmicrn it is excytsed frm the entercytes int the lacteals Released as a nascent chylmicrn particle because its functinally incmplete Once it reaches the plasma the nascent chylmicrn is rapidly mdified receiving aplipprtein-e & aplipprtein CII frm circulating HDL CII is required fr activatin f lipprtein lipase E is recgnized by hepatic receptrs and is required fr hepatic endcytsis f chylmicrn remnants

34 Degradatin f Chylmicrns Acquired ApCII n lipprtein particles induces activatin f LipPrtein lipase (LPL) Lipprtein Lipase Extracellular enzyme that is anchred by GPI ( glycsylated phsphatidyl-insitl ) t the capillary walls f mst tissues Heparan sulfate (leash) SO 4 keeps it in the lumen Fund mainly in cardiac and skeletal muscle tissues. NOT fund in adult liver/brain Muscle & Heart must always btain FAs even if lipid plasma levels are lw Can be activated by high insulin levels Functin: Hydrlyzes the TAG (w/i chylmicrns) FA + glycerl FA stred by adipse tissue and glycerl ges t the liver fr glyclysis r glucnegenesis Ap-lipprtein C is recycled back t HDL and nw yu are left with a chylmicrn remnant Chylmicrn remnant cntains chlesteryl esters, phsphlipids, ap-lipprtein B48 & E, and fat sluble vitamins bind t the receptrs n the liver and then are endcytsed. Remnants are hydrlyzed t their cmpnent parts Chlesterl and nitrgenus bases f phsphlipids can be recycled by the bdy Plasma Lipprteins Spherical macrmlecular cmplexes f lipids and specific prteins (either aplipprteins r apprteins)