De-orphanization of cytochrome P450 2R1: A microsomal vitamin D 25-hydroxylase

Jeffrey B. Cheng, Daniel L. Motola, David J. Mangelsdorf, David W. Russell

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Abstract

The conversion of vitamin D into an active ligand for the vitamin D receptor requires 25-hydroxylation in the liver and 1α-hydroxylation in the kidney. Mitochondrial and microsomal vitamin D 25-hydroxylase enzymes catalyze the first reaction. The mitochondrial activity is associated with sterol 27-hydroxylase, a cytochrome P450 (CYP27A1); however, the identity of the microsomal enzyme has remained elusive. A cDNA library prepared from hepatic mRNA of sterol 27-hydroxylase-deficient mice was screened with a ligand activation assay to identify an evolutionarily conserved microsomal cytochrome P450 (CYP2R1) with vitamin D 25-hydroxylase activity. Expression of CYP2R1 in cells led to the transcriptional activation of the vitamin D receptor when either vitamin D2, or D3 was added to the medium. Thin layer chromatography and radioimmunoassays indicated that the secosteroid product of CYP2R1 was 25-hydroxyvitamin D3. Co-expression of CYP2R1 with vitamin D 1α-hydroxylase (CYP27B1) elicited additive activation of vitamin D3, whereas co-expression with vitamin D 24-hydroxylase (CYP24A1) caused inactivation. CYP2R1 mRNA is abundant in the liver and testis, and present at lower levels in other tissues. The data suggest that CYP2R1 is a strong candidate for the microsomal vitamin D 25-hydroxylase.

Original languageEnglish (US)
Pages (from-to)38084-38093
Number of pages10
JournalJournal of Biological Chemistry
Volume278
Issue number39
DOIs
StatePublished - Sep 26 2003

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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