Stereochemistry of the Citrate‐Lyase Reaction

Abstract

Using a medium of tritiated water for the conversion of fumarate to malate and using a medium of deuterium oxide for the cleavage of citrate, chiral acetate was generated enzymically in the sequence fumarate → malate → oxaloacetate → citrate → acetate. Acetate of opposite chirality was produced in the same sequence by replacing fumarate and tritiated water by [2,3‐ 3 H 2 ]fumarate and ordinary water, respectively. The configuration of acetate generated in (1) was shown to be R , and the configuration of acetate generated in (2) was shown in to be S. It was concluded that citrate lyase cleaves citrate with inversion of configuration at the methylene group which becomes methyl.