Pyruvate Dehydrogenase

Pyruvate produced by glycolysis must be oxidized to acetate prior to entry into the citric acid cycle. The enzyme catalyzing this reaction is the pyruvate dehydrogenase complex. The overall reaction:

Pyruvate + NAD+ + CoA-SH <-> Acetyl-CoA + NADH + CO 2

is very energetically favorable ( = -33.5 kJ/mol) and is essentially irreversible in vivo. The reaction is somewhat involved. Catalysis of the reaction by the pyruvate dehydrogenase complex involves three enzymatic activities (below) and five coenzymes (CoA-SH, NADH, thiamine pyrophosphate, FAD, lipoic acid). The pyruvate dehydrogenase complex is a highly organized multienzyme assembly.

Enzymatic activities contained in the pyruvate dehydrogenase complex include:

> Pyruvate decarboxylase (E1)

> Dihydrolipoamide transacetylase (E2)

> Dihydrolipoamide dehydrogenase (E3)

See also: Pyruvate Dehydrogenase Complex, Glycolysis, Thiamine Pyrophosphate, Pyruvate Decarboxylase