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.