Isovaleryl-CoA dehydrogenase: demonstration in rat liver mitochondria by ion exchange chromatography and isoelectric focusing.

Abstract

There has been ambiguity concerning the specificity of the enzymes that dehydrogenate short branched-chain acyl-CoAs. It previously had been assumed that Isovaleryl-CoA is dehydrogenated by n-butyryl-CoA dehydrogenase (EC 1.3.99.2). Five short-chain acyl-CoA dehydrogenases (isovaleryl-CoA, n-butyryl-CoA, isobutyryl-CoA, n-octanoyl-CoA and glutaryl-CoA dehydrogenases) were fractionated from rat liver mitochondria by isoelectric focusing and DEAE-cellulose column chromatography. The isovaleryl-CoA dehydrogenase (EC 1.3.99.10) peak was almost completely separated from the peaks of n-butyryl-CoA- and n-octanoyl-CoA dehydrogenases by isoelectric focusing, and it was well separated from glutaryl-CoA dehydrogenase (EC 1.3.99.7) and n-octanoyl-CoA dehydrogenase by DEAE-cellulose column chromatography. The isovaleryl-CoA dehydrogenase peak partly overlapped that of n-butyryl-CoA and isobutyryl-CoA dehydrogenases in the latter procedure. Isovaleryl-CoA is apparently oxidized by a specific isovalery-CoA dehydrogenase. The other dehydrogenase peaks also demonstrated activity toward a single substrate, except that isobutyryl-CoA dehydrogenase activity could not be clearly resolved from n-butyryl-CoA dehydrogenase activity.