The 4 beta-methyl group of substrate does not affect the activity of lanosterol 14 alpha-demethylase (P-450(14)DM) of yeast: difference between the substrate recognition by yeast and plant sterol 14 alpha-demethylases.
Interaction of obtusifoliol and 24,28-dihydroobtusifoliol with yeast lanosterol 14 alpha-demethylase (P-450(14)DM) was studied to elucidate the role of the 4 beta-methyl group of substrate. P-450(14)DM of Saccharomyces cerevisiae catalyzed 14 alpha-demethylation of obtusifoliol. Apparent Vmax of obtusifoliol demethylation (15.4 nmol/min/nmol P-450) was similar to that of 24-methylene-24,25-dihydrolanosterol demethylation and was a little higher than those of lanosterol and 24,25-dihydrolanosterol demethylations. Apparent Km for obtusifoliol (12.0 microM) was higher than those for lanosterol and 24-methylene-24,25-dihydrolanosterol but was lower than that for 24,25-dihydrolanosterol. 24,28-Dihydroobtusifoliol was a very poor substrate for yeast P-450(14)DM. These facts suggest that the 4 beta-methyl group of sterol slightly affects the activity of yeast P-450(14)DM, while hydrogenation of a double bond in the sterol side-chain considerably impairs the activity. This finding is a contrast to the fact that the plant P-450(14)DM could not catalyze demethylation of sterols having 4 beta-methyl group, but favorably interacts with sterols having saturated side chain.
Aoyama
Y
Y
Faculty of Pharmaceutical Sciences, Mukogawa Women's University, Nishinomiya, Japan.
Yoshida
Y
Y
D002775:Cholestadienols / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004875:Ergosterol / Q000031:analogs & derivatives / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism*; D010944:Plants / Q000201:enzymology; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D058886:Sterol 14-Demethylase; D013379:Substrate Specificity
D002775:Cholestadienols; C074062:24,28-dihydroobtusifoliol; C008693:obtusifoliol; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D058886:Sterol 14-Demethylase; D004875:Ergosterol