A Stereochemical Probe of the Tetrahedral Intermediate in the Reactions of Acetyl-Coenzyme A Dependent Acetyltransferases

Abstract

A pair of isomeric acetyl-coenzyme A (acetyl-CoA) analogs have been prepared in which the thioester group is replaced with a secondary alcohol. The two isomers differ in stereoconfiguration of the secondary alcohol and were designed to mimic the two possible configurations of the tetrahedral intermediate or transition state in the reactions of acetyl-CoA dependent acetyltransferases. These two isomers were tested as inhibitors of chloramphenicol acetyltransferase and carnitine acetyltransferase, both of which have previously been predicted to form a tetrahedral intermediate which matches the configuration of the (S)-alcohol. The (S)-isomer was the more potent inhibitor of both enzymes, with Ki values 12-fold and 6-fold lower than the Ki values for the (R)-isomer. The (S)-isomer was also the more potent inhibitor of phosphate acetyltransferase, acetyl-CoA synthetase, and arylamine acetyltransferase, for which the stereochemistry of the tetrahedral intermediate was previously unknown. These results suggest ...