OXIDATIVE DECARBOXYLATION OF PYRUVATE Matrix of the mitochondria contains pyruvate dehydrogenase complex
The fate of glucose molecule in the cell Glucose Glucose-6- phosphate Pyruvate Glycogen Ribose, NADPH Pentose phosphate pathway Synthesis of glycogen Degradation of glycogen Glycolysis Gluconeogenesis LactateEthanol Acetyl Co A
Only about 7 % of the total potential energy present in glucose is released in glycolysis. Glycolysis is preliminary phase, preparing glucose for entry into aerobic metabolism. Pyruvate formed in the aerobic conditions undergoes conversion to acetyl CoA by pyruvate dehydrogenase complex. Pyruvate dehydrogenase complex is a bridge between glycolysis and aerobic metabolism – citric acid cycle. Pyruvate dehydrogenase complex and enzymes of cytric acid cycle are located in the matrix of mitochondria. OXIDATIVE DECARBOXYLATION OF PYRUVATE
Pyruvate translocase, protein embedded into the inner membrane, transports pyruvate from the intermembrane space into the matrix in symport with H + and exchange (antiport) for OH -. Entry of Pyruvate into the Mitochondrion Pyruvate freely diffuses through the outer membrane of mitochon- dria through the channels formed by transmembrane proteins porins.
Pyruvate dehydrogenase complex (PDH complex) is a multienzyme complex containing 3 enzymes, 5 coenzymes and other proteins. Conversion of Pyruvate to Acetyl CoA Pyruvate dehydrogenase complex is giant, with molecular mass ranging from 4 to 10 million daltons. Electron micrograph of the pyruvate dehydrogenase complex from E. coli.
Enzymes: E1 = pyruvate dehydrogenase E2 = dihydrolipoyl acetyltransferase E3 = dihydrolipoyl dehydrogenase Coenzymes: TPP (thiamine pyrophosphate), lipoamide, HS-CoA, FAD+, NAD+. TPP is a prosthetic group of B1; lipoamide is a prosthetic group of B2; and FAD is a prosthetic group of B3. The building block of TPP is vitamin B 1 (thiamin); NAD – vitamin B 5 (nicotinamide); FAD – vitamin B 2 (riboflavin), HS-CoA – vitamin B 3 (pantothenic acid), lipoamide – lipoic acid
Overall reaction of pyruvate dehydrogenase complex Pyruvate dehydrogenase complex is a classic example of multienzyme complex The oxidative decarboxylation of pyruvate catalized by pyruvate dehydrogenase complex occurs in five steps.