Metabolism of lipids. Szerkesztette: Fekete Veronika

Transcription

1 Metabolism of lipids

2 Transport of free fatty acid in the plasma ketone bodies C 2 + H 2 phospholipid synthesis Ac-CoA FFA oxidation ketone bodies FREE FATTY ACID (FFA) fatty acid-albumin triacyl glycerol fatty acid ADIPSE TISSUE Hormonsensitive lipase Ketone bodies fatty acid C 2 + H 2 Phospholipid, triacylglycerol synthesis RGANS skeletal muscle heart muscle kidney

3 Composition of lipoproteins Surface: Core components: apoproteins phospholipids polar triacylglycerols cholesterol-esthers apolar cholesterol Triacylglycerol, cholesterol-esther Apoprotein cholesterol phospholipid

4 Characteristics of lipoproteins Lipoprotein Density Protein content (%) Lipid content (%) important lipid Apoprotein Chylomikron (CM) Triacylglycerol B-48, C-II, C-III, E VLDL Triacylglycerol B-100, C-I, C-II, C-III, E IDL Triacylglycerol cholesterolesther B-100, E LDL cholesterolesther B-100 HDL phospholipid, cholesterolesther A-I, A-II, C-I, C-II, C-III, E

5 Structure of cholesterol Basic structure: sterol ring (ciklopentanoperhydrofenantren) Hydrofobic, non-water soluble 70 % of it exits in cholesterol-esther form

6 Role of cholesterol it can be found in all cell types origin: exogen: (food intake) endogen: intracellular de novo synthesis role: regulation of membrane fuidity precursor for steroid hormon synthesis precursor for bile acid synthesis precursor for vitamin D 3

7 2 NADPH+H + 2 NADP + Synthesis of cholesterol I. Tiolase Acetoacetyl-CoA HMG-CoAsynthase HMG-CoA HMG-CoAreductase 3,3-dimethylallylpirophosphate Isomerase phosphomevalonatekinase Mevalonate- 5-pirophospho decarboxylase Mevalonatekinase Mevalonate ADP ATP 3-izopentenylpirophosphate ADP ATP ATP ADP 5-pirophosphomevalonate 5-phosphomevalonate

8 Synthesis of cholesterol II. Prenyltransferase 3-izopentenylpirophosphate 3,3-dimethylallylpirophosphate Prenyltransferase Isomerase + NADPH+H + Geranyl-pirophosphate Farnesylpirofoszfát 2 NADP + 3-izopentenylpirophosphate Squalenesynthase Lanosterol Squalenemonooxygenase Squalene-epoxidelanosterol-cyclase Squalene-2,3-epoxide Squalene

9 Synthesis of cholesterol III. NAD + NADH+H + Lanosterol 3 -hydroxisteroid- 24-reductase Dihydrolanosterol 3 -hydroxisteroid- 8, 7-isomerase NADP + NADPH+H + Cholesterol 3 -hydroxisteroid- 7-reductase 7-dehydrocholesterol

10 Regulation of cholesterol synthesis Plasma cholesterol (LDL) EXGEN CHLESTERL chylomicron CHLESTERL + INSULIN TRIJDTIRNINE Ac-CoA HMG-CoAreductase Mevalonate GLUCAGN CHLESTERL KRTISL BILE ACIDS Drugs (Statins)

11 Introduction Ketone bodies: -hydroxi-butyrate acetoacetate acetone concentration in blood stream < 0,2 mm Characteristics: formation from Acetyl-CoA water soluble molecules produced mainly by liver, less by alternative energy sources for peripherial tissues

12 Synthesis of ketone bodies Tiolase 2 acetyl-coa CoA-SH Ac-CoA + H 2 CoA-SH Acetoacetyl-CoA 3-hydroxi-3-methyl-glutaryl-CoA (HMG-CoA) HMG-CoA-liase HMG-CoAsynthase -hydroxibutyratedehydrogenase Acetil-CoA -hydroxi-butyrate NAD + NADH+H + acetoacetate C 2 acetone

13 Utilisation of ketone bodies -hydroxi-butyrate NAD + NADH + H + Acetoacetate Succynyl- CoA Acetoacetate: succynyl-coa transferase Succynate CoA-SH 2 Acetyl-CoA Tiolase Acetoacetyl-CoA

14 Utilisation of ketone bodies Peripheral tissues: heart muscle skeletal muscle kidney brain 2 Ac-CoA acetoacetyl- CoA TCA cycle succynate CoAtransferase acetoacetate acetoacetate succynyl-coa hydroxi-butyrate hydroxi-butyrate

15 Utilisation of fatty acids Tissues are not supported by fatty acids: nervous tissue red blood cell adrenal medulla Fatty acids are predominant energy supply for heart and skeletal muscle Utilisation of fatty acids by tissues mainly depends on actual need

16 Transport of fatty acids to mitochondria CoA SH Fatty acid ATP ACTIVATIN AMP + PP i Malonyl-CoA Acyl-CoA Carnitine-acyltransferase I. CoA SH Carnitine Acyl-carnitine CITPLASM CARNITINE CARRIER INNER MITCHNDRIAL MEMBRANE Carnitine Acyl-carnitine Acyl-CoA Carnitine-acyltransferase II. CoA SH -oxidation MITCHNDRIA

17 xidation of Even numbered fatty acids oxidation

18 Metabolism of propionyl-coa H 3 C CH 2 C S CoA Propionyl-CoA HC 3 - ATP ADP + P i C - H 3 C CH C S CoA Methyl-malonyl-CoA cofactor: biotin Vitamin-B 12 Propionyl-CoAcarboxylase Methyl-malonil- CoA-mutáz - C CH 2 CH 2 Succynyl-CoA CH 2 C S CoA cofactor: B 12 Citric acid cycle

19 xidation of fatty acids with cis conformation I. H 3 C (CH 2 ) n CH 2 H C H cis- 2-enoyl-CoA H 2 C C S CoA 1. Hydratase H H 3 C (CH 2 ) n CH 2 C CH 2 C S CoA H -D-hydroxy-acyl-CoA H 3 C H (CH 2 ) n CH 2 C H -L-hydroxy-acyl-CoA Epimerase CH 2 C S CoA -oxidation

20 xidation of fatty acids with cis conformation II. H 3 C (CH 2 ) n H H C C CH 2 C S CoA cis- 3-enoyl-CoA Izomerase H H 3 C (CH 2 ) n CH C H C C S CoA trans- 2-enoyl-CoA -oxidation

21 Additional steps of oxidation of linolic acid (18:2 9,12) H 3 C H 3 C H 3 C H 3 C (CH 2 ) 4 (CH 2 ) 4 NADPH+H + NADP + (CH 2 ) 4 (CH 2 ) 4 H C 5. H C 5. H C CH 2 CH 2 C S CoA trans 4 enoyl-coa H C H 1. C C C S CoA H trans- 2-cis 4 enoyl-coa CH 2 H 1. C C CH 2 C S CoA H trans- 3-enoyl-CoA CH 2 5. CH 2 H 1. C C C S CoA H trans- 2-enoyl-CoA 1. Acyl-CoAdehydrogenase Reductase Isomerase -oxidation

22 Saturated fatty acids carbon chain and terminal carboxyl group the carbon chain does not contain any double bonds flexible, linear structure General structure: H 3 C n. (CH 2 ) x CH 2 CH 2 CH 2 CH short chain: n=2 5 middle chain: n=6 11 long chain: n=12 26

23 Unsaturated fatty acids Fatty acid Number of carbons Number of double bonds Position of double bonds Palmitic acid 16 0 Palmitoleic acid Stearic acid 18 0 leic acid Linoic acid* ,12-6 Linolenic acid* ,12,15-3 Arachidonic acid ,8,11,14-6 *: essential fatty acids

24 Linoic Linolsav: acid -6 zsírsav Essential fatty acids Linolenic Linolénsav: acid -3 zsírsav Role: synthesis of eikozanoids synthesis of poli-unsaturated fatty acids taking part in formation of biological membranes ccurence: linoic acid: plant oils linolenic acid: sea fish

25 rigin of components required for fatty acid synthesis Acetyl-CoA: from carbohydrate metabolism (reaction catalysed by pyruvatedehydrogenase enzyme complex) NADPH: direct oxidation of glucose reaction catalysed by malic enzyme in cytoplasm reaction catalysed by az isocitrate-dehydrogenase

26 Transport of acetyl-coa to the cytoplasm MITCHNDRIUM -ketoglutarate oxaloacetate isocitrate ATP Acetyl-CoA CITRATE CYTPLASM HS CoA oxaloacetate CITRATE Acetyl-CoA ATP ADP + P i ATP-citrate-liase

27 Source of NADPH Fatty acid synthesis pyruvate + HC 3 - citrate citrate Acetyl-CoA NADPH+H + NADP + Malic enzyme Malatedehydrogenase ATP-citrateliase oxaloacetate NADH+H + NAD + malate

28 de novo synthesis of fatty acids all fatty acids synthesised from palmitic acid Catalytic anzyme: fatty acid synthase 2 subunit 7 different protein with biological activity 2 SH-groups for binding of acyl- and acetyl groups in each subunits ACP (acyl carrier protein): binding of 4 -foszfopantetheine Enzymes: acyl-transferase malonyl-coa-acp-transzacylase (malonyl-transferase) -ketoacyl-acp-synthase (kondenzáló enzim) enzymes redukáló enzimek tioészteráz

29 Model of fatty acid synthase DMAIN I. DMAIN II. DMAIN III. Acyl-transferase Malonyl-transferase Ketoacyl synthase Reducing enzymes Thioesterase SUBUNIT I. SH ACP SH SH ACP SH Thioesterase Ketoacyl synthase Reducing enzymes Acyl-transferase Malonyl-transferase SUBUNIT II.

30 Synthesis of fatty acid Ketoacyl synthase Ketoacyl synthase Ketoacyl synthase Ketoacyl synthase Ketoacyl synthase S SH SH S S C C C CH 3 CH 2 CH 2 CH 2 CH 2 condensation reducing translocation next condensation CH 3 CH steps 3 malonyl-coa C 2 C 2 CH 3 CH 3 C - C CH 2 C - CH 2 CH 2 CH 2 CH 2 C C C C S S S SH S ACP ACP Szerkesztette: ACP Fekete Veronika ACP ACP

31 Reducing steps in fatty acid synthesis ACP ACP S S C CH 2 C CH 3 NADPH + H + NADP + H C CH 2 CH CH 3 Acetoacethyl-S-ACP ketoacyl- ACP-reductase -hidroxy-butiryl-acp hidroxy-acyl- ACP-dehydratase ACP ACP S S C CH CH CH 3 NADPH + H + NADP + C CH 2 CH 2 CH 3 Crotonil-S-ACP enoyl-acpreductase Butiryl-S-ACP

32 Regulation of fatty acid synthesis R C S CoA + HC 3 - Acetyl-CoAcarboxylase - C CH 2 C S CoA ATP ADP+P i Main step of fatty acid synthesis: acetyl-coa-carboxylase Cofactor: biotin binding of C 2 with usage of ATP Regulation: allosteric activator: citrate it helps in formation of active polimer allosteric inhibitor: malonyl-coa, palmitoyl-coa they inhibit the formation of active polimer transcription of the enzyme adapts to the fed-state of the body

33 Characterisation of arachidonic acid synthesis precursors are linoleic and linolenic acids 2-acyl position of a glicerophospholipids is saturated by arachidonic acid free arachidonic acid concentration of cytosol is very limited Committed step of eicosanoid biosynthesis is deliberation of arachidonic acod from phospholipids Arachidonic acid CH

34 Deliberation of arachidonic acid from phospholipids 1. Phospholipase A 2 (PLA 2 ) a) high molecular weight PLA 2 Specific for arachidonic acid Increase in the intracellular Ca 2+ concentration support its translocation to the plasma membrane b) low molecular weight PLA 2 Not specific for arachidonic acid Glucocorticoids inhibit it 2. Phospholipase C (PLC) and DAG-lipase Arachidonic acid deliberated from diacyl glycerol by DAG lipase which originated from TG by a PLC platelets

35 xidation of arachidonic acid in the cells Arachidonic acid Cyclooxygenasepathway Lipoxygenasepathway Cytochrom P450 Epoxygenase-pathway Prostaglandins (PG) Thromboxanes (Tx) Hydroperoxieicosatetraenoic acids (HPETE) Hydroxyeicosatetraenoic acids (HETE) Leukotrienes (LT) Epoxieicosatetraenoic acids (EET) Lipoxins

36 xidation of arachidonic acid Phosphatidyl choline Phosphatidyl inositol PLC PLA 2 5-LP Leukotrienes: LTA 4, LTB 4, LTC 4, LTE 4, LTF 4, LXA 4 15-LP Leukotrienes: LXA, LXB DAG: diacyl-glycerol CX: cyclooxygenase Tx: thromboxane LP: lipoxygenase Arachidonic acid CX Txsynthase PGsynthse PGH 2 CX Prosztaglandins: PGE 2, PGD 2, PGF 2, PGA 2, PGB 2 PGH 2 Prostacycline -synthase CX PGH 2 DAGlipase Prostacyclines: PGI 2, PGF 2 Thromboxanes: TXA 2, TXB 2

37 The cyclooxygenase-pathway Arachidonic acid PGI CX PGG 2 PG-hidroperoxidase Prostacyclin synthetase Thromboxane-synthetase PGH-PGE-izomerase PGH-PDF-reductase TxA 2 PGE 2 PGF 2 PGH-PGDizomerase PGH 2 PGD 2

38 lipoxigenase Arachidonic acid 5-HPETE 2 5-lipoxigenase epoxihydrolase LTA 4 glutathione 5-HETE LTB 4 Glu Gly LTC 4 dihetederivatives gluthatione-stranszferase -glutamyltranspeptidase LT D 4 LT E 4 LT F 4 dipeptidase Glu

39 Action of anti-inflammatory drugs Membrane phospholipids NSAID Pl: Aspirin - cyclooxygenase phospholipids Arachidonic acid - steroids Prostaglandin endoperoxids 5-HPETE LT A 4 Tx A 2 prostaglandins LT C 4 LT D 4 5-HETE LT B 4 LT E 4