Properties of a Yeast Cytochrome P‐450‐Containing Enzyme System which Catalyzes the Hydroxylation of Fatty Acids, Alkanes, and Drugs

Abstract

The growth of Candida tropicalis on tetradecane causes the induction of a cytochrome P‐450‐containing enzyme system which catalyzes the hydroxylation of fatty acids, hydrocarbons and drugs. When the cells are broken by treatment with a French pressure cell, the cytochrome P‐450 is obtained in an apparently soluble form. The enzyme system was resolved into three components: cytochrome P‐450, NADPH‐cytochrome P‐450 reductase, and a heat‐stable lipid fraction, all of which are necessary, along with NADPH and molecular oxygen, for the conversion of laurate to ω‐hydroxylaurate. NADH alone is almost completely inactive but causes a doubling of the activity when present along with a saturating level of NADPH. The yeast reductase and lipid fractions may be replaced by corresponding fractions obtained from rat liver microsomes. The effect of various phospholipids on the hydroxylation activity was investigated, and a yeast lysophosphati‐dylethanolamine fraction was shown to be most effective as judged by laurate hydroxylation. The yeast cytochrome P‐450 is not readily autoxidizable, as shown by experiments in which it was reduced extensively by NADPH in the presence of phospholipid and the reductase under aerobic conditions.