Lanosterol 14 alpha-demethylase (cytochrome P-45014DM): modulation of its enzyme activity by cholesterol feeding

Regulation of the activity of lanosterol 14 alpha-demethylase (cytochrome P-45014DM) by dietary cholesterol was studied in rats. In male rats fed a 3% cholesterol diet for 1 and 4 weeks, the activity of 24,25-dihydrolanosterol 14 alpha-demethylase was decreased in the liver. The cytochrome P-45014DM protein content detected by immunoblotting was also decreased by cholesterol feeding. These results demonstrate that dietary cholesterol acts as a repressive factor for lanosterol 14 alpha-demethylase. Further, the activity was enhanced by preincubation with phosphatase of the enzyme solution from both the control and cholesterol fed rats at the same rate. This result suggests that regulation of the activity involves phosphorylation of this enzyme.