title: Vitamin D hydroxylases.
abstract: There are three mixed function oxidases which catalyze hydroxylations of vitamin D and its derivatives. These include the hepatic mitochondrial or microsomal vitamin D3-25-hydroxylase and the two renal mitochondrial enzymes which further hydroxylate 25-hydroxyvitamin-D3 (25-OH-D3) to form 24R,25-dihydroxyvitamin D3 (24,25(OH)2D3) and 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], the primary steroid hormonal derivative of vitamin D3. All three enzymes are cytochrome P450 dependent. The two renal mitochondrial enzymes are regulated, usually in a reciprocal fashion. The intracellular signalling systems involved in this regulation include 1,25(OH)2D3 itself and both protein kinases A and C. Recent progress has been made in the purification and cloning of the vitamin D3-25-hydroxylase and the 25-OH-D3-24-hydroxylase. When the 25-OH-D3-1-hydroxylase is purified and cloned, efforts which have thus far been frustrated by its low abundance, fertile new ground for the study of the regulation of vitamin D metabolism at the molecular level will be opened up.
authors.affiliation: Department of Biochemistry, University of California, Riverside 92521.
authors.forename: H L
authors.initials: HL
authors.lastname: Henry
mesh_terms: D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000378:metabolism*; D000818:Animals; D053493:Cholestanetriol 26-Monooxygenase; D003577:Cytochrome P-450 Enzyme System; D006801:Humans; D013250:Steroid Hydroxylases / Q000378:metabolism; D014807:Vitamin D / Q000378:metabolism*; D065668:Vitamin D3 24-Hydroxylase
chemical_list: D014807:Vitamin D; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; C506831:CYP27A1 protein, human; D053493:Cholestanetriol 26-Monooxygenase; D065668:Vitamin D3 24-Hydroxylase; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase