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16 Cards in this Set
- Front
- Back
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Regulation of respiratory chain and aerobic phosphorylation
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availability of O2
• ratio of NADH / NAD+ (proton gradien on an inner mitoch. membr.) • availability of ADP for ATP synthesis • uncoupling proteins (proton gradien) |
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Regulation of citric acid cycle
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• availability of substrates
• consumption of products (NAD, FAD) • Ratio ATP/ADP • • citrate synthase • isocitrate dehydrogenase (key enzyme) • 2-oxoglutarate dehydrogenase |
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Regulation of pyruvate dehydrogenase reaction (PDH)
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• interconversion of PDH: phosphorylated form is inactive, dephosphorylated form is active (= principal regulation mechanism)
• competitive inhibition by products (acetyl-CoA and NADH) • • I: ↑ NADH / NAD+, acetyl-CoA • A: insulin |
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Regulation of glycolysis
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1) hexokinase
• 2) glucokinase • 3) 6-phosphofructo-1-kinase (6-PFK-1) (key enzyme) • 4) pyruvate kinase • Regulation of PPK: • A: ↑AMP / ATP, fructose-2,6-bisphosphate (related to ↑insulin / glucagon), insulin (induction) • I: ↑ ATP / AMP, citrate, acidic pH |
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Regulation of gluconeogenesis
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1) pyruvate carboxylase
• 2) phosphoenolpyruvate carboxykinase • 3) fructose-1,6-bisphosphatase • 4) glucose-6-phosphatase • general regulation (Ad 1) - 4)): • A: cortisol a glusagon (induction) • I: insulin (repression) • • Ad 3): I: ↑ AMP / ATP, fructose-2,6-bisphosphate (related to ↑ insulin/glucagon) • Ad1):A:AcCoA |
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Regulation of glycogen metabolism
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• 1) glycogen phosphorylase (degradation of glycogen)
• 2) glycogen synthase (synthesis of glycogen) • • Ad 1): • A: glucagon, adrenaline (phosphorylation), ↑AMP / ATP, Ca2+ (in muscle) • I: insulin, glucose-6-P • • Ad 2): • A: insulin (induction), glucose-6-P • I: glucagon, adrenaline (phosphorylation) |
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Regulation of pentose cycle
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• NADPH / NADP+ inhibits regulatory enzymes: glucose-6- phosphate dehydrogenase and 6- phosphogluconate dehydrogenase
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Regulation of lipolysis
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• hormone sensitive lipase (adipocytes) adipocytech)
• A: catecholamines, glucagon, ACTH (phosphorylation) • I: insulin • lipoprotein lipase (endothelium surface) • A: insulin, apolipoprotein C-II |
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Regulation of beta-oxidation
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Regulation of beta-oxidation
• supply of fatty acids (see regulation of lipolysis) • velocity of transport of fatty acids into a mitochondrion: carnitine acyltransferase I is inhibited by malonyl-CoA ratio of FAD/FADH2 and NAD+/NADH (more reduced forms - inhibition) • consumption of acetyl-CoA by subsequent reactions |
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Regulation of ketogenesis
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• production of acetyl-CoA (= substrate)
• the regulation is related to regulation of lipolysis and beta- oxidation |
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Regulation of fatty acid synthesis
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• 1) acetyl-CoA carboxylase (key regulatory enzyme)
• 2) synthase of fatty acids • • Ad 1) • A: citrate, insulin, low-fat, energy rich, high- saccharide diet (induction) I: acyl-CoA (C16 – C18), glucagon (phosphorylation, repression), lipid-rich diet, starvation (repression) |
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Regulation of TAG synthesis
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• availability of acyl-CoA as a
consequence of both fatty acid synthesis de novo and releasing of fatty acids from TAG • • lipoprotein lipase (related to storage of TAG in adipocytes) • A: insulin, apolipoprotein C-II • • phosphatidic acid phosphatase • A: steroid hormones (induction) |
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Regulation of cholesterol synthesis
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• HMG-CoA reductase
• A: insulin, tyroxine (induction) • I: cholesterol, glucagon (repression), oxosterols (repression), statins |
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Regulation of urea cycle
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• induction of the enzymes by protein-rich diet or by metabolic changes during starvation (degradation of amino acids - ↑ Gln)
• in relation to ABB: acidosis - inhibition of the urea cycle (salvage of HCO3-) • • Carbamoylphosphate synthetase I • A:N-acetylglutamate • N-acetylglutamate synthetase • A:arginine |
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Regulation of nucleotide synthesis
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• PRPP-synthetase
• I: purine and pyrimidine nucleotides (nucleoside diphosphates and nucleoside triphosphates) – feedback inhibition • Nucleoside diphosphate reductase • A: nucleoside triphosphates • I: deoxyadenosine triphosphate (dATP) |
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Regulation of nucleotide synthesis
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• Key regulatory enzymes:
• glutamine-PRPP-amidotransferase (purines) • A: PRPP • I: IMP, GMP, AMP (allosterical inhibition) • carbamoylphosphate synthetase II (pyrimidines) • A: PRDP, ATP • I: UTP |
