The Requirement for Coenzyme a in the Enzymatic Synthesis of Hippuric Acid

Previous studies from this laboratory have shown that p-aminohippuric acid is formed from p-aminobenzoic acid and glycine by liver slices (1) and homogenates under aerobic conditions, or anaerobically with adenosinetriphosphate (ATP) as the source of energy (2, 3). Similar observations on the synthesis of hippuric acid have been briefly reported (4). These studies suggested the format,ion of a high energy intermediate, the nature of which is still unknown. Among the different possibilities considered (5), the formation of an acyl phosphate appeared most probable. Unpublished work by R. W. McGilvery of this laboratory had shown that the synthesis of p-aminohippuric acid occurs in extracts of acetone powder of rat liver. It was found in the present study that the same extracts also catalyze hippuric acid formation from benzoic acid plus glycine in the presence of ATP. This provided us with a more suitable system for the study of the mechanism of the reaction. The experiments reported in the present paper show that benzoyl phosphate is not the high energy intermediate in hippuric acid synthesis, and further that coenzyme A is required for the condensation of benzoic acid with glycine.