OXIDATIVE DECARBOXYLATION OXIDATIVE DECARBOXYLATION OF PYRUVATE 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 OXIDATIVE DECARBOXYLATION OF PYRUVATEPYRUVATE
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 MitochondrionPyruvate 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 dehydrogenaseE2 = dihydrolipoyl acetyltransferaseE3 = 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 B1 (thiamin); NAD – vitamin B5 (nicotinamide); FAD – vitamin B2 (riboflavin), HS-CoA – vitamin B3 (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.