METABOLISM Sri Widia A Jusman Department of Biochemistry & Molecular Biology FMUI 1
METABOLISM Process of how cells acquire, transform, store and use energy Study of the chemistry, regulation and energetics of the reactions in biological cells All organisms use the same general pathway for extraction and utilization of energy 2
In human metabolism is a series of changes that a substance undergoes after absorption from gastrointestinal tract, used for synthesis of tissue component (anabolism) or breakdown (catabolism) or altered and eliminated from the body metabolic process regulated by nerve and hormonal control 3
METABOLISM CATABOLISM - pathway for breakdown / oxidation of substances, produced energy ANABOLISM - pathway for synthesis of substances, need energy Food digest Small mol abs anabolism ATP Prot, CH, fat catabolism CO 2 + H 2 O 4
CATABOLISM Degradative pathway of complex organic molecules ( fats, carbohydrate and proteins ) to a simpler molecule ( lactate, pyruvate, CO 2, H 2 O and NH 3 ) Characterized by oxidation reactions, released free energy from foodstuff, captured in the form of ATP Catabolic process release the potential energy from food and collect it in the reactive intermediate 5
Stages of catabolism Stage I breakdown of macromolecules to building blocks - proteins amino acids - triacylglycerols fatty acids + glycerol - polysaccharides glucose Stage II amino acids, fatty acids, monosaccharides are oxidized to acetyl CoA some energy released and captured in the form of NADH and ATP acetyl CoA is a common catabolism product of protein, CH and fat 6
Stage III acetyl CoA enter citric acid cycle, oxidized to CO 2 oxidative phosphorylation in respiratory chain - produced ATP & H 2 O 7
Protein CH Lipid AA glucose fatty acid NH 3 Acetyl CoA CO 2 Krebs cycle e- RC H 2 O + ATP Catabolism Convergent 8
ANABOLISM Construction of large, complex biomolecules from smaller precursor molecules ( amino acids proteins, pyruvate glucose, nucleotides DNA, etc) Energy supplied by ATP, NADH / NADPH from catabolism Anabolic process use the energy stored in ATP 9
STAGES OF ANABOLISM 3 stages catabolism simple metabolites macromolecules need energy ( ATP, NADPH ) divergent CH Oxaloacetate / pyruvate / lactate monosaccharide polysaccharide PROTEIN acetyl CoA / pyruvate / α-ketoacids + NH 3 amino acids proteins FAT Acetyl CoA fatty acids triacylglycerols 10
Anabolism and catabolism linked together ATP - universal carrier of biochemical energy The recycling of ATP is the central theme of metabolism 11
Stage I Protein CH Lipid Macro mol A A glucose Fatty acid + glycerol ATP ATP Pyruvate ATP building block Stage II Stage III ATP Acetyl CoA Krebs cycle NH 3 ATP H 2 O CO 2 Common catab product Catab end-product 12
CARBOHYDRATE METABOLISM 13
Carbohydrate 70%-80% of dietary intake Function energy source for metabolic processes 3 monosaccharides absorbed amylum intestine glucose sucrose fructose lactose galactose Glucose, fructose, galactose after absorbed from intestine - were transported to the liver Liver convert fructose, galactose glucose CH used as a energy by cells - glucose 14
Liver some parts of glucose were oxidized ATP (through glycolysis for liver cells ) stored as glycogen (through glycogenesis) transport out to extrahepatic tissues to be oxidized ATP (glycolysis for brain, erythrocytes, muscle, adipose tissue) excess intake of carbohydrate stored as fat (through lipogenesis) 15
Transport of glucose into the tissues - need insulin (except liver cells) brain - absolutely need glucose as source of energy glucose CO 2 + H 2 O + ATP blood glucose dizziness, headache coma death erythrocytes - absolutely need glucose glucose pyruvate lactate + ATP 16
Muscle can use different sources of energy - blood glucose - muscle glycogen - fattty acids glucose pyruvate lactic acid + ATP (anerobic) CO 2 + H 2 O + ATP (aerobic) Adipose tissue - use glucose as source of energy or stored as triacylglycerols glucose CO 2 + H 2 O + ATP (glycolysis) triacylglycerols ( lipogenesis ) 17
METABOLIC PATHWAYS of CH Glycolysis HMP ( Hexose Mono Phosphate ) shunt Glycogenesis Glycogenolysis Gluconeogenesis Uronic acid pathway Amino sugar pathway Citric acid cycle ( Krebs cycle ) 18
GLYCOLYSIS major metabolic pathway of glucose - produced energy for cell / tissues occurred in cytosol of all cells Step I - glucose undergoes phosphorylation - by hexokinase or glukokinase to produce G6-P G 6-P - important intermediate - related with - HMP shunt - glycogenesis - glycogenolysis - gluconeogenesis 19
DIFFERENCES HEXOKINASE - GLUKOKINASE HK GK - present in all cells - only in liver and kidney - constitutive enzyme - inducible enzyme - inhibited by its product - not inhibited by its ( G 6-P ) product - affinity for glucose - affinity for glucose (Km for glucose ) ( Km for glucose ) - can phosphorylate - only phosphorylate another hexoses glucose - function: for maintained - function: for lowering supply of energy to the blood glucose after tissues meal 20
GLYCOLYSIS (Embden-Meyerhoff pathway) Major metabolic pathway of glucose produced energy 1 mol glucose ( 6 C ) split into 2 mol pyruvates (3 C ) through several steps Occurred in cytosol of all cells Can proceed in - aerobic condition - anaerobic condition 21
GLYCOLYTIC PATHWAY (Embden-Meyerhoff pathway) Glucose + ATP glucose 6-P + ADP Glucose 6-P fructose 6-P Fructose 6-P + ATP fructose 1,6-BP + ADP Fructose 1,6-BP di-ohacetone-p + glyceraldehide 3-P Glyceraldehide 3-P + Pi + NAD 1,3-bisphosphoglycerate + NADH + H+ 1,3-bisphosphoglycerate + ADP 3-P glycerate + ATP 3-P glycerate 2-P glycerate 2-P glycerate P-enolpyruvate + H2O P-enol pyruvate + ADP pyruvate + ATP 22
AEROBIC GLYCOLYSIS occur under aerobic condition end product : pyruvate under aerobic condition, pyruvate will be oxidized further in mitochondria to acetyl CoA to produce CO 2 + H 2 O + ATP via citric acid cycle energy yield / mol glucose : 38 ATP gluc pyruvate pyruvate acetyl CoA CO 2 + H 2 O + ATP 23
Aerobic Glycolysis 24
ANAEROBIC GLYCOLYSIS occur under anerobic condition in all cells and in erythrocytes end product : lactate pyruvate reduced to lactate by enzyme lactate dehydrogenase ( LDH ), need NADH energy yield : 2 ATP/ mol oxidized glucose HK/GK LDH Gluc G 6P 2 pyruvate 2 Lactate NADH + H + NAD + 25
GLYCOLYSIS IN ERYTHROCYTE end product : always lactate ( although the surrounding medium is aerobic ) produced 2,3-bisphosphoglycerate (2,3- BPG) - facilitate removal of oxygen from hemoglobin in the tissues where po 2 is low 26
ATP Glucose Glycogen Glucose 6-P HK GLYCOLYSIS Fructose 6-P ATP PFK Fructose 1,6-BP Glyceraldehide 3-P NAD + GAPDH NADH + H + 1,3-BP Glycerate Di-OH acetone P ATP 3-P Glycerate Lactate LDH ATP PK pyruvate Cytosol CO2 malate fumarate oxaloacetate TCA cycle citrate pyruvate PDH Acetyl CoA α KG Mitochondria 27
OXIDATIVE DECARBOXYLATION OF PYRUVATE TO ACETYL COA catalyzed by pyruvate dehydrogenase (PDH ) complex, need coenzymes : - coenzyme A ( CoA ) - lipoic acid - thiamine pyrophosphate ( TPP ) - flavin adenine dinucleotide ( FAD ) - niacinamide adenine dinucleotida ( NAD ) PDH Pyruvate acetyl CoA + CO 2 FAD, NAD + CoA, lipoic acid, TPP FADH, NADH + H + RC CO2 + ATP 28
KREBS CYCLE (citric acid cycle, tricarboxylic acid cycle ) series of reactions formed a cycle occur in matrix mitochondria common metabolic pathway for oxidation of carbohydrate, fat and protein convert to acetyl CoA or intermediates of citric acid cycle catabolic role also play role in gluconeogenesis, transamination / deamination, lipogenesis anabolic role AMPHIBOLIC ROLE OF KREBS CYCLE 29
TCA / Krebs cycle 30
glucose Fatty acid Amino acid Acetyl CoA oxaloacetate citrate malate isocitrate fumarate 2H 2H α-ketoglutarate succinate NAD 2H succynil CoA 2H Fp Catabolic role of TCA Cycle KoQ Sit b Sit c P P Oxidative phosphorylation Sit aa3 P H 2 O 31
Gluconeogenesis Amino acids Acetyl CoA Oxaloacetate Citrate Fatty acids Malate α-ketoglutarate Succinyl CoA amino acids Heme Anabolic role of TCA cycle 32
HMP SHUNT (Pentose phosphate pathway) alternative oxidative pathway for glucose, besides glycolysis Function : not to produce energy, but to produce - NADPH for synthesis of fatty acid, steroid hormone, protect cells from oxidative damage - ribose for synthesis of nucleic acids (DNA/RNA) occur in cytosol of liver tissues, mammary tissues during lactation, gonades, adrenal cortex, liver, erythrocytes. 33
HMP shunt - 2 steps: I. Dehydrogenation and decarboxylation of G 6-P to ribulose 5-P catalyzed by enzyme G 6-P dehydrogenase (G6P DH) NADP NADPH Glucose G 6-P Ribulose 5-P G6P DH 34
II. Resynthesis of G 6-P from ribulose 5-P under series of reaction, catalyzed by enzymes transketolase and transaldolase, need coenzyme TPP ( measurement of activity of transketolase - for diagnosis of thiamine deficiency ) Transketolse, transaldolase Ribulose 5-P Glucose 6-P TPP 35
GLYCOGENESIS (synthesis glycogen from glucose) occur in liver and muscle tissues glycogen - stored form of carbohydrate in animal (analog to amylum in plants) - polymer of glucose with 1,4-glycosidic bonding ( between C1 of one glucose with C4 of next glucose ) - at branch point, 1,6-glycosidic bonding Enzymes - glycogen synthetase - branching enzymes 36
Protein kinase A - glucagon Glycogen synthase (inactive) ADP ATP Glycogen synthase (active) Protein phosphatase Pi + insulin Glycogen UDPGlucose PPi UTP G 1-P G 6-P Glycogen synthesis Glucose 37
1,4-glycosidic bonding Glycogen primer Glycogen synthase Branching enzyme Biosynthesis of glycogen 1,6-glycosidic bonding 38
Glycogen α1 4 & α1 6 glucosyl units Pi α1 4 glucosyl units Branching enzyme Insulin - Glycogenolysis Glycogen primer Glycogen synthase - camp + phosphorylase UDPG + Glukagon Debranching enzyme Glycogen synthesis UTP GK G 1-P G 6-P ADP G 6-Pase ATP glucose Free glucose (from debranching enzyme) 39
GLYCOGENOLYSIS Liver glycogen convert to glucose (Glycogen G 1P G 6 P glucose) if there is need for glucose of the tissues ( in fasting) Muscle glycogenolysis to supply energy for muscle iself end product: glucose 6-P because muscle does not contain enzyme G 6Pase glycogenolysis continues with glycolysis in muscle 40
Liver glycogenolysis to maintained blood glucose between normal range for energy Important for supply of glucose to particular tissues - especially brain, erythrocytes end product: free glucose, diffuse into blood circulation which then uptake by tissues Enzymes : - Glycogen phosphorylase - Glycogen transferase - debranching enzyme 41
Pi Free glucose Glycogen phosphorylase Glucan transferase Debranching enzyme Steps of glycogenolysis 42
GLUCONEOGENESIS (synthesis of glucose from non-ch precursors) occur when there is no sufficient carbohydrate in diet intake glucose absolutely need as a source energy for certain tissues most active tissue - liver, kidney gluconeogenesis process - reversal of glycolysis process, except on certain points, need certain enzymes ( key enzymes ) 43
substrate for gluconeogenesis lactate ( by lactate dehydrogenase) glycerol ( by glycerokinase ) glycogenic amino acids ( via intermediates of TCA cycle - fumarat, oxaloacetate, α-ketoglutarate ) 44
G6Pase F1,6BPase Glucose G 6P F 6P F1,6BP Glycolysis Pyr carboxykinase Pyr carboxylase PEP Pyruvate Acetyl CoA Glycerol Lactate, Amino acid Amino acid Gluconeogenesis Oxaloacetate Malate TCA Citrate Amino acid 45
Cori cycle Lactic acid formed by glycolysis in muscle (anaerobic) and erythrocyte transported to the liver & kidney reformed to glucose - enter circulation uptake by muscle tissues Glucose alanine cycle Alanine (from degradation of protein in muscle tissue during starvation) transported to the liver reformed to glucose enter circulation uptake by muscle tissues transamination to alanine 46
47
REGULATION OF BLOOD GLUCOSE Carbohydrate currency of the body - glucose postprandial ( after meal ) glucose concentration increased up to 110-140 mg/ dl - rapidly taken-up by all tissues - in a few hour restored to fasting level blood glucose level - stimulate insulin secretion from pancreas - glucose enter cells - pathways for glucose consumption of tissues - glycolysis, glycogenesis, HMP shunt - blood glucose level back to normal 48
even in fasting there is always a minimum concentration of glucose ( 60-90 mg/dl ) exercise/fasting blood glucose level - stimulate glucagon secretion from pancreas, epinephrine from adrenal medulla - glycogenolysis, gluconeogenesis - blood glucose level back to normal Insulin & glucagon - regulate blood glucose level 49
Insulin play a central role in regulating blood glucose Secreted as a direct response to hyperglycemia facilitate uptake of glucose into extrahepatic tissues Stimulate the liver to store glucose as glycogen Stimulate the glycolysis, HMP shunt Stimulate the lipogenesis in adipose tissues 50
Glucagon Opposes the action of insulin Secreted as a response to hypoglycemia Activate gluconeogenesis and glycogenolysis 51
52