title: A rapid assay for 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D 24-hydroxylase.
abstract: A rapid method for the measurement of the 24-hydroxylated metabolites of 25-hydroxy[26,27-3H]vitamin D3 and 1,25-dihydroxy[26,27-3H]vitamin D3 has been developed. This measurement has, in turn, made possible a rapid assay for the 24-hydroxylases of the vitamin D system. The assay involves the use of 26,27-3H-labeled 1,25-dihydroxyvitamin D3 or 25-hydroxyvitamin D3 as the substrate and treatment of the enzyme reaction mixture with sodium periodate, which specifically cleaves the 24-hydroxylated products between carbons 24 and 25, releasing tritiated acetone. The acetone is measured after its separation from the labeled substrate by using a reversed-phase cartridge. The results obtained with this assay were validated by comparison with the results obtained with a well-established high-performance liquid chromatography assay. The activity of the enzyme determined by both methods was equal. This assay has been successfully used for the rapid screening of column fractions during purification of the enzyme and in the screening for monoclonal antibodies to the 24-hydroxylase.
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison 53706.
authors.forename: M
authors.initials: M
authors.lastname: Burgos-Trinidad
authors.forename: A J
authors.initials: AJ
authors.lastname: Brown
authors.forename: H F
authors.initials: HF
authors.lastname: DeLuca
mesh_terms: D015650:24,25-Dihydroxyvitamin D 3 / Q000378:metabolism; D000096:Acetone / Q000378:metabolism; D000818:Animals; D001894:Borohydrides; D002112:Calcifediol / Q000378:metabolism*; D002645:Chickens; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003577:Cytochrome P-450 Enzyme System; D006887:Hydroxycholecalciferols / Q000378:metabolism; D010084:Oxidation-Reduction; D010504:Periodic Acid / Q000378:metabolism; D013250:Steroid Hydroxylases / Q000378:metabolism*; D013997:Time Factors; D014316:Tritium; D065668:Vitamin D3 24-Hydroxylase
chemical_list: D001894:Borohydrides; D006887:Hydroxycholecalciferols; D014316:Tritium; D010504:Periodic Acid; D000096:Acetone; D015650:24,25-Dihydroxyvitamin D 3; C013721:1,24,25-trihydroxyvitamin D3; C025364:sodium borohydride; D003577:Cytochrome P-450 Enzyme System; C009288:metaperiodate; D013250:Steroid Hydroxylases; D065668:Vitamin D3 24-Hydroxylase; D002112:Calcifediol