title: Two species of cytochrome P-450 involved in ergosterol biosynthesis of yeast.
abstract: Discrimination of cytochrome P-450 involved in delta 22-desaturation of ergosta-5,7-dien-3 beta-o1 (P-450(22)-DS) from that involved in lanosterol 14 alpha-demethylation (P-450(14)-DM) in ergosterol biosynthesis was investigated with microsomes of several strains of Saccharomyces cerevisiae. In mutant N22 which is partially defective in the delta 22-desaturation, the 14 alpha-demethylation was not blocked. In contrast, mutant SG1 which is known to lack the 14 alpha-demethylation showed a significant activity of the delta 22-desaturation. The delta 22-desaturation activity was markedly increased upon aerobic adaptation of yeast cells but the 14 alpha-demethylation was not affected. Buthiobate, a specific inhibitor of P-450(14)-DM, and rabbit antibodies against P-450(14)-DM did not inhibit the delta 22-desaturation activity at all. It is evident from the obtained observations that these phenomena are not explainable in terms of NADPH-cytochrome P-450 reductase. These results indicate that P-450(22)-DS is different from P-450(14)-DM in molecular species.
mesh_terms: D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004875:Ergosterol / Q000096:biosynthesis*; D044943:Fatty Acid Desaturases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*
chemical_list: D003577:Cytochrome P-450 Enzyme System; D044943:Fatty Acid Desaturases; C039609:delta-22 fatty acid desaturase; D004875:Ergosterol