The barrel structure of pyruvate kinase is denoted as Pyruvate Kinase Barrel (IPR015793). Pyruvate kinase (PK) catalyzes the final step of glycolysis, which involves the conversion of phosphoenolpyruvate to pyruvate. It also phosphorylates ADP to ATP. L (liver), R (erythrocytes), M1 (muscle, heart, and brain), and M2 (early embryonic tissues) are the four tissue-specific isozymes. ATP inhibits M1-type PK (muscle, brain), while F1,6BP and alanine have no effect. This is relevant to muscle and brain function, but not liver function. Pyruvate kinase C-terminal (IPR015795) is the C-terminal of pyruvate kinase.