Impact of carbon source and growth conditions on carnitine acetyltransferase inSaccharomyces cerevisiae

Abstract

In Candida tropicalis growing on n-alkane, the substrate is oxidized to the corresponding fatty acid, which is then degraded by fl-oxidation, yielding acetyl-coenzyme A (CoA). This B-oxidation was shown to be localized in the peroxisomes [1]. The transport of acetyl groups out of the peroxisomes proceeds via acetylcarnitine. A key enzyme of this shuttle is carnitine acetyltransferase (CAT, EC 2.3.1.7), an enzyme that is present in hydrocarbon-assimilating yeasts [1,2]. In Saccharomyces cerevisiae, CAT was described and functionally related to acetyl group transport through the mitochondrial membrane [3]. However, the need for acetyl group transfer out of the mitochondria depends on the conditions under which the yeast cells are grown. This becomes especially important in the case of S. cerevisiae where different physiological states are well known [4]. The present paper reports on the influence of carbon source and growth conditions on CAT activity of the cells. The conditions considered were growth on glucose at derepressed and repressed states and on ethanol as the carbon source.