Pyruvate dehydrogenase is a complex composed of three enzymes, responsible for catalyzing the irreversible reaction of pyruvate decarboxylation to acetyl coenzyme A, distributed in the inner membrane of mitochondria. Enzymes differ from phosphorylases in that they come in inactive (phosphorylated) and active (dephosphorylated) forms. A variety of allosteric regulators regulate the conversion of the two enzyme forms and are influenced by hormonal activity.
