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|Section2= |Section3= }} 24,25-Dihydroxycholecalciferol, also known as 24,25-dihydroxyvitamin D3 and (24''R'')-hydroxycalcidiol (abbreviated as 24(R),25-(OH)2D3),〔("Nomenclature of Vitamin D. Recommendations 1981. IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN) )" reproduced at the Queen Mary, University of London website. Retrieved 21 March 2010.〕 is a compound which is closely related to 1,25-dihydroxyvitamin D3, the active form of vitamin D3, but like vitamin D3 itself and 25-hydroxyvitamin D3 is inactive as a hormone both ''in vitro'' and ''in vivo''. It was identified by Michael F. Holick. ==Formation and significance== 24,25-dihydroxyvitamin D3 is formed from 25-hydroxyvitamin D3 by the action of P450cc24 (25-hydroxyvitamin D3-24-hydroxylase), which appears to be "a multicatalytic enzyme catalyzing most, if not all, of the reactions in the C-24/C-23 pathway of 25-OH-D3 metabolism." It has been proposed that 24,25-dihydroxyvitamin D3 is a metabolite of 25-hydroxyvitamin D3 which is destined for excretion.〔 It is not known whether the compound might also have some physiologically significant activity. Some evidence of a possible receptor has been obtained. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「24,25-Dihydroxycholecalciferol」の詳細全文を読む スポンサード リンク
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