Subcellular distribution of enzymes in the yeast saccharomycopsis lipolytica, grown on n-hexadecane, with special reference to the omega-hydroxylase.

The subcellular localization of the omega-hydroxylase of Saccharomycopsis lipolytica was assessed by the analytical fractionation technique, originally described by de Duve C., Pressman, B.C., Gianetto, R., Wattiaux, R. and Appelmans, F., and hitherto little, if at all, applied to yeasts. Protoplasts were separated in six fractions by differential centrifugation. Some of these fractions were further fractionated by density gradient centrifugation. The distribution of omega-hydroxylase and 15 other constituents chosen as possible markers of its subcellular entities. (1) Mitochondria were characterized by particulate malate dehydrogenase, particulate Antimycin A-insensitive NADH-cytochrome c reductase, oligomycin-sensitive and K+-stimulated ATPase pH 9. (2) Most if not all of the catalase and urate oxidase is peroxisomal. (3) Free ribosomes account for most RNA. (4) Nucleoside diphosphatase is for the first time reported in a yeast and appears to belong to an homogeneous population of small membranes. (5) The soluble compartment contains magnesium pyrophosphatase, alkaline, 5'-nucleotidase and part of the NADH-cytochrome c reductase. Latent arylesterase and ATPase pH 7 have an unspecific distribution. Alkaline phosphodiesterase I has not been detected.