Oxidation of 2-keto-4-hydroxyglutarate by pig heart and Escherichia coli [alpha]-ketoglutarate dehydrogenase complex

Abstract

Enzyme preparations from pig heart and Escherichia coli have been found to catalyze a NAD+- and CoASH-dependent oxidation of 2-keto-4-hydroxyglutarate. Several independent lines of evidence indicate that 2-keto-4-hydroxyglutarate is a substrate for the well-known [alpha]-ketoglutarate dehydrogenase complex of the citric acid cycle. The evidence includes (a) a constant ratio of specific activity values for the two substrates throughout purification, (b) identical elution profiles from a Ca3(PO4)2 gel-cellulose column, (c) the same sucrose density sedimentation patterns, (d) similar responses in controlled heat inactivation studies, and (e) identical pH-activity curves.