De-orphanization of cytochrome P450 2R1: a microsomal vitamin D 25-hydroxilase

J Biol Chem. 2003 Sep 26;278(39):38084-93. doi: 10.1074/jbc.M307028200. Epub 2003 Jul 16.

Abstract

The conversion of vitamin D into an active ligand for the vitamin D receptor requires 25-hydroxylation in the liver and 1alpha-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 1alpha-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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 25-Hydroxyvitamin D3 1-alpha-Hydroxylase / chemistry
  • Amino Acid Sequence
  • Animals
  • Cholestanetriol 26-Monooxygenase
  • Cytochrome P-450 Enzyme System / genetics
  • Cytochrome P450 Family 2
  • Humans
  • Mice
  • Microsomes / enzymology*
  • Molecular Sequence Data
  • RNA, Messenger / analysis
  • Steroid Hydroxylases / chemistry
  • Steroid Hydroxylases / genetics*
  • Vitamin D3 24-Hydroxylase

Substances

  • RNA, Messenger
  • Cytochrome P-450 Enzyme System
  • Steroid Hydroxylases
  • Cytochrome P450 Family 2
  • CYP2R1 protein, human
  • CYP27A1 protein, human
  • Cholestanetriol 26-Monooxygenase
  • Cyp27a1 protein, mouse
  • CYP24A1 protein, human
  • Cyp24a1 protein, mouse
  • Vitamin D3 24-Hydroxylase
  • 25-Hydroxyvitamin D3 1-alpha-Hydroxylase

Associated data

  • GENBANK/AY323817
  • GENBANK/AY323818