Expression and Characterization of CYP52 Genes Involved in the Biosynthesis of Sophorolipid and Alkane Metabolism from Starmerella bombicola

Three cytochrome P450 monooxygenase CYP52 gene family members were isolated from the sophorolipid-producing yeast Starmerella bombicola (former Candida bombicola), namely, CYP52E3, CYP52M1, and CYP52N1, and their open reading frames were cloned into the pYES2 vector for expression in Saccharomyces cerevisiae. The functions of the recombinant proteins were analyzed with a variety of alkane and fatty acid substrates using microsome proteins or a whole-cell system. CYP52M1 was found to oxidize C-16 to C-20 fatty acids preferentially. It converted oleic acid (C-18:1) more efficiently than stearic acid (C-18:0) and linoleic acid (C-18:2) and much more effectively than alpha-linolenic acid (C-18:3). No products were detected when C-10 to C-12 fatty acids were used as the substrates. Moreover, CYP52M1 hydroxylated fatty acids at their omega- and omega-1 positions. CYP52N1 oxidized C-14 to C-20 saturated and unsaturated fatty acids and preferentially oxidized palmitic acid, oleic acid, and linoleic acid. It only catalyzed omega-hydroxylation of fatty acids. Minor omega-hydroxylation activity against myristic acid, palmitic acid, palmitoleic acid, and oleic acid was shown for CYP52E3. Furthermore, the three P450s were coassayed with glucosyltransferase UGTA1. UGTA1 glycosylated all hydroxyl fatty acids generated by CYP52E3, CYP52M1, and CYP52N1. The transformation efficiency of fatty acids into glucolipids by CYP52M1/UGTA1 was much higher than those by CYP52N1/UGTA1 and CYP52E3/UGTA1. Taken together, CYP52M1 is demonstrated to be involved in the biosynthesis of sophorolipid, whereas CYP52E3 and CYP52N1 might be involved in alkane metabolism in S. bombicola but downstream of the initial oxidation steps.