Acyloin condensation reactions of pyruvic oxidase.

Almost all enzymes capable of decarboxylating pyruvate have been shown to catalyze DPT’-dependent condensation reactions yielding acyloins such as AMC (l-7). Recent work of Schweet and coworkers (8) has demonstrated that in animal tissues these condensations are due to the activity of pyruvic oxidase. Purified preparations of pyruvic oxidase from pigeon breast muscle have the same ratio of acyloin formed to pyruvate oxidized as do crude homogenates. In preparations of cr-carboxylase from wheat germ there is a constant ratio of decarboxylation to AMC synthesis throughout a 2700-fold purification (5), and the different activities have identical requirements for DPT and a metallic ion. Preparations of animal pyruvic oxidase can utilize diacetyl as an analogue of pyruvate. Schweet and coworkers (8) have shown pyruvic oxidase to be identical with the diacetyl mutase first described by Green and coworkers (9). Studies in this laboratory have revealed a new pathway for the bacterial dissimilation of diacetyl (10). In this system diacetyl is quantitatively converted to acetic acid and diacetylmethylcarbinol (Equation 1) in a reaction similar to that involving the formation of or-acetolactate from pyruvate by AMC-producing bacteria (Equation 2).