Stereospecific metabolism of isomeric epoxyoctadecanoic acids in the lactone-producing yeast Sporidiobolus salmonicolor.

The metabolic course of four isomeric epoxyfatty acids derived from oleic-, elaidic-, (Z)-, and (E)-vaccenic acids in the lactone-producing yeast, Sporidiobolus salmonicolor, was studied by using the deuterium-labeled precursors. Dihydroxy-, hydroxyoxo-, and hydroxy fatty acids as well as gamma-lactones were identified as metabolic intermediates. Quantitative analysis of the label content and estimation of the enantiomeric composition of the lactones established that, in the first step, the racemic epoxyfatty acids were enantiospecifically hydrolyzed by an epoxide hydrolase. During the subsequent metabolism, the stereochemical orientation of the hydroxy groups of the dihydroxyfatty acids were modified by an oxidation/reduction step.