Pyruvate dehydrogenase kinase is a part of the pyruvate dehydrogenase complex. It plays a regulatory role by phosphorylating three specific E1 serine residues (when active), resulting in loss of activity of the pyruvate dehydrogenase complex.

NADH and acetyl-CoA both activate the kinase. The serines are dephosphorylated by a specific enzyme called pyruvate dehydrogenase phosphatase.