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  • Title: 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.
    Author: Aoyama Y, Yoshida Y.
    Journal: Biochem Biophys Res Commun; 1992 Mar 31; 183(3):1266-72. PubMed ID: 1567403.
    Abstract:
    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.
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