Pyruvate Dehydrogenase Complex

One source of acetyl-CoA molecules for the citric acid cycle is oxidative decarboxylation of pyruvate, catalyzed by the pyruvate dehydrogenase complex. The complex is composed of three enzymes

> 1. Pyruvate decarboxylase (E1)

> 2. Dihydrolipoamide transacetylase (E2)

> 3. Dihydrolipoamide dehydrogenase (E3)

and five coenzymes

> 1. Thiamine Pyrophosphate (TPP)

> 2. Lipoic Acid - lipoamide

> 3. FAD

> 4. NAD+

> 5. CoASH

The reaction mechanism is described here and is depicted in Figure 14.10.

The pyruvate dehydrogenase complex resembles the -ketoglutarate dehydrogenase complex (AKGDH). The three enzyme activities are analogous and the five coenzymes are the same. The pyruvate dehydrogenase complex also catalyzes a similar reaction - oxidative decarboxylation of an -keto acid. The pyruvate dehydrogenase complex differs from the AKGDH in being regulated allosterically and and controlled via covalent modification.

See also: Pyruvate Oxidation, Pyruvate Dehydrogenase Complex Regulation

INTERNET LINK: -Keto Acid Complexes - A Review