Stereochemical Course of the Maleate Hydratase Reaction

Abstract

Abstract Equilibration of maleate in D2O with a partially purified preparation of maleate hydratase from rabbit kidney resulted in the formation of d-malate containing 1 atom of stably bound deuterium per molecule. The enzyme therefore catalyzes a stereospecific addition to the double bond of maleate. The product of the enzymatic hydration in D2O was examined by nuclear magnetic resonance spectroscopy. In addition, the monodeuteriosuccinate obtained by chemical reduction of the deuterated d-malate was analyzed for its optical rotatory properties. The absolute configuration of the enzymatically deuterated malate was thus established and corresponded to the structure d-malate-3-d-(3-R). It was concluded that the over-all reaction catalyzed by maleate hydratase is trans.