title: Kinetics of kidney mitochondrial 25-hydroxycholecalciferol-1 alpha-hydroxylase in vitamin D-repleted weanling guinea pigs.
abstract: Kinetics of vitamin D-repleted guinea pig kidney mitochondrial 25-hydroxycholecalciferol-1 alpha-hydroxylase were studied. Omission of malate, source of mitochondrial reducing equivalents, abolished the 1 alpha-hydroxylase activity as well as the degradation of 1 alpha, 25-dihydroxycholecalciferol [1,25(OH)2D3], indicating that both functions shared elements of a common pathway. Preincubation of the mitochondrial preparation in presence of 10 nM 1,25(OH)2D3 for 15 min protected the labeled 1,25(OH)2D3 from degradation. Under these conditions an apparent Km of 605 nM and a Vmax of 40 pmol/30 min/mg mitochondrial protein were observed. These data show that this particular mammalian model may be used to study the modulation of mammalian 1 alpha-hydroxylase activity.
mesh_terms: D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000378:metabolism*; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D006168:Guinea Pigs; D007668:Kidney / Q000201:enzymology*; D007700:Kinetics; D008297:Male; D013058:Mass Spectrometry; D008928:Mitochondria / Q000201:enzymology* / Q000648:ultrastructure; D013250:Steroid Hydroxylases / Q000378:metabolism*; D014807:Vitamin D / Q000502:physiology*; D014808:Vitamin D Deficiency / Q000201:enzymology
chemical_list: D014807:Vitamin D; D013250:Steroid Hydroxylases; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase