Steric Course of Reaction Catalyzed by the Enoyl Acyl‐Carrier‐Protein Reductase of Escherichia coli

Abstract

The steric course of the reaction catalyzed by Escherichia coli enoyl acyl‐carrier‐protein reductase was studied. trans‐2‐[2‐2H1]Decenoic and trans‐2‐[3‐2H1]decenoic acids were synthesized and converted to the corresponding decenoyl thiol esters with CoA or acyl carrier protein. These deuterium‐labeled decenoyl thiol esters were incubated with purified enoyl acyl‐carrier‐protein reductase in the presence of NADPH or NADH. The unlabeled trans‐2‐decenoyl thiol esters were incubated with enoyl acyl‐carrier‐protein reductase in the presence of (4S)‐[4‐2H1]NADH. The unlabeled decenoyl thiol esters were also incubated with the enzyme in 2H2O. The decanoic acids formed in the above incubations were extracted and subjected to the action of acyl‐CoA oxidase which had been previously shown to catalyze the anti elimination of the pro‐2R and pro‐3R hydrogens of acyl‐CoA. The resulting products, 2‐decenoyl‐CoAs, were converted to methyl esters and their deuterium contents were analyzed by gas chromatography/mass spectrometry. The results suggested that the reduction catalyzed by E. coli enoyl acyl‐carrier‐protein reductase occurs by a syn addition of hydrogen via a 2‐Re, 3‐Si attack on the double bond. Copyright © 1981, Wiley Blackwell. All rights reserved