25-Hydroxycholecalciferol-1-hydroxylase
Year: 1972
Type: article
Abstract: The subcellular distribution and properties of an enzyme system responsible for hydroxylation of 25-hydroxycholecalciferol (25-OHD3) to 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) in chicken kidney have been described. The enzyme, which is highly specific for 25-OHD3 since it does not hydroxylate cholecalciferol or dihydrotachysterol, is located in the mitochondria and has a pH optimum of 7.4 and an apparent Km of 2.2 x 10-6 m. At 8.34 x 10-7 m 25-OHD3, 1,25-(OH)2D3 production is linear with mitochondrial protein concentrations of up to 8 mg per ml. Enzyme activity is maximal in Tris-acetate buffer and requires Mg2+, oxygen, and a source of reduced pyridine nucleotide, which in intact mitochondria is provided by malate or succinate. The succinate-supported hydroxylation is dependent upon electron transport and oxidative phosphorylation. The 25-OHD3-1-hydroxylase is inhibited by carbon monoxide, metapyrone, p-chloromercuribenzoate, and diphenyl-p-phenylenediamine. The enzyme is also inhibited by its product, 1,25-(OH)2D3. It is, however, much more strongly inhibited competitively by 25-hydroxydihydrotachysterol, a close analog of 1,25-(OH)2D3.
Source: Journal of Biological Chemistry
Institution: University of Wisconsin–Madison
Language: English
Topic: Vitamin D Research Studies
Subfield: Pathology and Forensic Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W1602537057