title: An alternative pathway of vitamin D metabolism. Cytochrome P450scc (CYP11A1)-mediated conversion to 20-hydroxyvitamin D2 and 17,20-dihydroxyvitamin D2.
abstract: We report an alternative, hydroxylating pathway for the metabolism of vitamin D2 in a cytochrome P450 side chain cleavage (P450scc; CYP11A1) reconstituted system. NMR analyses identified solely 20-hydroxyvitamin D2 and 17,20-dihydroxyvitamin D2 derivatives. 20-Hydroxyvitamin D2 was produced at a rate of 0.34 mol x min(-1) x mol(-1) P450scc, and 17,20-dihydroxyvitamin D2 was produced at a rate of 0.13 mol x min(-1) x mol(-1). In adrenal mitochondria, vitamin D2 was metabolized to six monohydroxy products. Nevertheless, aminoglutethimide (a P450scc inhibitor) inhibited this adrenal metabolite formation. Initial testing of metabolites for biological activity showed that, similar to vitamin D2, 20-hydroxyvitamin D2 and 17,20-dihydroxyvitamin D2 inhibited DNA synthesis in human epidermal HaCaT keratinocytes, although to a greater degree. 17,20-Dihydroxyvitamin D2 stimulated transcriptional activity of the involucrin promoter, again to a significantly greater extent than vitamin D2, while the effect of 20-hydroxyvitamin D2 was statistically insignificant. Thus, P450scc can metabolize vitamin D2 to generate novel products, with intrinsic biological activity (at least in keratinocytes).
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Tennessee Health Science Center, Memphis, TN 38163, USA. aslominski@utmem.edu
authors.forename: Andrzej
authors.initials: A
authors.lastname: Slominski
authors.forename: Igor
authors.initials: I
authors.lastname: Semak
authors.forename: Jacobo
authors.initials: J
authors.lastname: Wortsman
authors.forename: Jordan
authors.initials: J
authors.lastname: Zjawiony
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Blazej
authors.initials: B
authors.lastname: Zbytek
authors.forename: Robert C
authors.initials: RC
authors.lastname: Tuckey
mesh_terms: D015652:25-Hydroxyvitamin D 2 / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D000616:Aminoglutethimide / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000378:metabolism*; D004872:Ergocalciferols / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D006887:Hydroxycholecalciferols / Q000737:chemistry* / Q000378:metabolism; D015603:Keratinocytes / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D011401:Promoter Regions, Genetic; D011498:Protein Precursors / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar
chemical_list: C512457:17,20-dihydroxyvitamin D2; C512456:20-hydroxyvitamin D2; D004872:Ergocalciferols; D006887:Hydroxycholecalciferols; D011498:Protein Precursors; D000616:Aminoglutethimide; D015652:25-Hydroxyvitamin D 2; C032253:involucrin; D002786:Cholesterol Side-Chain Cleavage Enzyme