title: Identification of lanosterol 14 alpha-methyl demethylase in human tissues.
abstract: Lanosterol 14 alpha-methyl demethylase was investigated in human tissues using a radio-HPLC assay to detect the 4,4-dimethyl-5 alpha-cholesta-8, 14-dien-3 beta-ol (diene) metabolite. The sequence of events leading to the demethylated product in human liver microsomes involves the conversion of the diol to the aldehyde followed by diene formation. Enzyme activity displayed a greater than 10 fold variation among the 9 liver samples studied. Kinetic parameters were determined and shown to differ between two separate liver samples. Addition of inhibitors of yeast lanosterol 14 alpha demethylase, ketoconazole and miconazole, resulted in extensive inhibition of formation of the demethylated metabolite. The enzyme, detected in microsomes isolated from human kidney and lymphocytes, also catalyzed the conversion of dihydrolanosterol to oxylanosterol intermediates and the diene. The presence of this enzyme in microsomes from various human tissues suggests that it may play a role in cellular regulation of cholesterol synthesis.
authors.affiliation: University of New Mexico, College of Pharmacy, Albuquerque 87131.
authors.forename: J L
authors.initials: JL
authors.lastname: Raucy
authors.forename: S J
authors.initials: SJ
authors.lastname: Carpenter
authors.forename: J M
authors.initials: JM
authors.lastname: Trzaskos
mesh_terms: D000328:Adult; D002851:Chromatography, High Pressure Liquid; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis / Q000378:metabolism*; D005260:Female; D006801:Humans; D007668:Kidney / Q000201:enzymology*; D007672:Kidney Cortex / Q000201:enzymology; D007700:Kinetics; D008214:Lymphocytes / Q000201:enzymology; D008297:Male; D008861:Microsomes / Q000201:enzymology*; D008862:Microsomes, Liver / Q000201:enzymology*; D008875:Middle Aged; D010088:Oxidoreductases / Q000032:analysis / Q000378:metabolism*; D058886:Sterol 14-Demethylase
chemical_list: C548418:CYP51A1 protein, human; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D058886:Sterol 14-Demethylase