Peroxisomal and mitochondrial carnitine acetyltransferases in alkane-grown yeast Candida tropicalis

Two types of carnitine acetyltransferases (EC 2.3.1.7) were first isolated from a microorganism, alkane-grown yeast Candida tropicalis. Carnitine acetyltransferase activity was induced in the alkane-grown cells, reaching about twenty times higher than that in the glucose-grown cells. Localization of the enzyme activity was demonstrated, at least, in peroxisomes (microbodies), profusely occurred in the alkane-grown cells, and in mitochondria. Peroxisomal and mitochondrial carnitine acetyltransferases could be separated using the method of DEAE-Sephacel column chromatography and both types were found to exist in the alkane-grown cells of C. tropicalis. Each carnitine acetyltransferase was purified using Sephadex G-200, Sepharose 6B, DEAE-Sephacel and Blue-Sepharose CL-6B. In DEAE-Sephacel chromatography, peroxisomal carnitine acetyltransferase was eluted below 0.15 M KCl concentration and mitochondrial carnitine acetyltransferase above 0.15 M KCl concentration. Except for the localization, little difference was observed in their kinetic properties, substrate specificity and so on. These two carnitine acetyltransferase preparations were only specific to acetyl and propionyl groups, the substrate specificity not being so broad as that of carnitine acetyltransferase obtained from mammalian tissues. Roles of these carnitine acetyltransferases in alkane metabolism in yeast are also discussed.