biotin

A heat-stable coenzyme that acts as a carrier of carboxyl groups in many important metabolic reactions. An example is the oxidative decarboxylation of pyruvate to acetyl CoA, in which biotin acts as an intermediate carrier of the carboxyl group before it is released as free carbon dioxide. It is usually tightly bound to the enzyme for which it is the cofactor. Biotin is one of the B group of vitamins.