title: Synthesis of 1,25-dihydroxycholecalciferol and 24,25-dihydroxycholecalciferol by calvarial cells. Characterization of the enzyme systems.
abstract: The synthesis of 1,25-dihydroxycholecalciferol [1,25(OH)2D3] and 24,25-dihydroxycholecalciferol [24,25(OH)2D3] from 25-hydroxycholecalciferol [25(OH)D3] has previously been shown to occur in cells isolated from bone. The main findings of the present study are that the enzyme systems which catalyse these syntheses are: (1) active at 'in vitro' substrate concentrations over the range of 2-50 nM; (2) regulatable in a complex way by 1,25(OH)2D3, 24,25(OH)2D3, 25,26-dihydroxycholecalciferol and 25(OH)D3, but not by cholecalciferol ('vitamin D3'); and (3) have relatively short half-lives (approx. 5 h).
mesh_terms: D015650:24,25-Dihydroxyvitamin D 3; D000818:Animals; D001842:Bone and Bones / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D002117:Calcitriol / Q000096:biosynthesis*; D002478:Cells, Cultured; D002642:Chick Embryo; D004100:Dihydroxycholecalciferols / Q000096:biosynthesis*; D006207:Half-Life; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D014176:Protein Biosynthesis; D011691:Puromycin / Q000494:pharmacology
chemical_list: D004100:Dihydroxycholecalciferols; D015650:24,25-Dihydroxyvitamin D 3; D011691:Puromycin; D006899:Mixed Function Oxygenases; D002117:Calcitriol