Pyruvate Kinase

Pyruvate kinase catalyzes the last step in the process of glycolysis, conversion of the high-energy intermediate, phosphoenolpyruvate (PEP) to pyruvate accompanied by conversion of ADP + Pi to ATP (See Figure).

> PEP + H+ + ADP <=> Pyruvate + ATP

This reaction is one of two substrate level phosphorylations in glycolysis (the other is catalyzed by phosphoglycerate kinase). The enzyme is a key control point for glycolysis.

Pyruvate kinase is inhibited by ATP, activated by fructose-1,6-bisphosphate (feedforward activation), and inhibited by acetyl-CoA. It is also responsive to hormonally-regulated phosphorylation in the liver - the phosphorylated form of the enzyme is less active. Alanine is also an inhibitor of the enzyme.

Human deficiency of erythrocyte pyruvate kinase leads to excessive blood levels of glycolytic intermediates and, importantly 2,3 bisphosphoglycerate.

Glucagon represses synthesis of pyruvate kinase.

Previous step of glycolysis

See also: Enzymes of Glycolysis, Molecules of Glycolysis, Glycolysis, Pyruvate Kinase Regulation, Pyruvate Kinase Isozymes, Substrate Level Phosphorylation, Phosphoglycerate Kinase, Action of Glucagon

INTERNET LINKS:

> 1. RasMol Image of Pyruvate Kinase (slow)

> 2. Glycolysis/Gluconeogenesis