Pyruvate decarboxylation

Pyruvate dehydrogenase complex reaction

Pyruvate decarboxylation or pyruvate oxidation, also known as the link reaction, is the conversion of pyruvate into acetyl-CoA by the enzyme complex pyruvate dehydrogenase complex.

The reaction may be simplified as:

1 Pyruvate + 1 NAD⁺ + CoA → 1 Acetyl-CoA + NADH + CO₂ + H⁺

Pyruvate oxidation is the step that connects glycolysis and the Krebs cycle. In glycolysis, a single glucose molecule (6 carbons) is split into 2 pyruvates (3 carbons each), hence link reaction occurs twice for each glucose molecule to produce a total of 2 acetyl-CoA molecules, which can then enter the Krebs cycle.

Energy-generating ions and molecules such as amino acids and carbohydrates enter the Krebs cycle as acetyl coenzyme A and oxidize in the cycle. The pyruvate dehydrogenase complex (PDC) catalyzes the decarboxylation of pyruvate resulting in the synthesis of acetyl-CoA, CO₂, and NADH. In eukaryotes, this enzyme complex regulates pyruvate metabolism and ensures homeostasis of glucose during the absorptive and post-absorptive state metabolism. As the Krebs cycle occurs in the mitochondrial matrix, the pyruvate generated during glycolysis in the cytosol is transported across the inner mitochondrial membrane by a pyruvate carrier under aerobic conditions.