Induction and subcellular localization of enzymes participating in propionate metabolism in Candida tropicalis

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Abstract
Candida tropicalis, a representative alkane- and higher fatty acid-utilizing yeast, can grow on propionate used as sole carbon and energy source. Initial pH of the medium markedly affected the growth of the yeast on propionate. In propionate-grown cells, several enzymes associated with peroxisomes and/or participating in propionate metabolism were induced in connection with the appearance of the characteristic peroxisomes. Acetate-grown cells of this yeast had only few peroxisomes, while alkane-grown cells contained conspicuous numbers of the organelles. As compared with alkane-grown cells, some specific features were observed in peroxisomes and enzymes associated with the organelles of propionate-grown cells: The shape of peroxisomes was large but the number was small; unlike localization of catalase in peroxisomes of alkane-grown cells, the enzyme of propionate-grown cells was mainly localized in cytoplasm; as for carnitine acetyltransferase localized almost equally in peroxisomes and mitochondria in alkane-grown cells, propionate-grown cells contained mainly the mitochondrial type enzyme. A propionate-activating enzyme, which was different from acetyl-CoA synthetase, was also induced in cytoplasm of propionate-grown cells. The role of carnitine acetyltransferase and the propionate-activating enzyme in propionate metabolism is discussed in comparison with the role of carnitine acetyltransferase and acetyl-CoA synthetase in acetate metabolism.