Metabolism of vitamin D by human microsomal CYP2R1.
The activation of vitamin D requires 25-hydroxylation in the liver and 1alpha-hydroxylation in the kidney. However, it remains unclear which enzyme is relevant to vitamin D 25-hydroxylation. Recently, human CYP2R1 has been reported to be a potential candidate for a hepatic vitamin D 25-hydroxylase. Thus, vitamin D metabolism by CYP2R1 was compared with human mitochondrial CYP27A1, which used to be considered a physiologically important vitamin D(3) 25-hydroxylase. A clear difference was observed between CYP2R1 and CYP27A1 in the metabolism of vitamin D(2). CYP2R1 hydroxylated vitamin D(2) at the C-25 position while CYP27A1 hydroxylated it at positions C-24 and C-27. The K(m) and k(cat) values for the CYP2R1-dependent 25-hydroxylation activity toward vitamin D(3) were 0.45microM and 0.97min(-1), respectively. The k(cat)/K(m) value of CYP2R1 was 26-fold higher than that of CYP27A1. These results strongly suggest that CYP2R1 plays a physiologically important role in the vitamin D 25-hydroxylation in humans.
Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kitashirakawa, Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan.
Raku
R
Shinkyo
Toshiyuki
T
Sakaki
Masaki
M
Kamakura
Miho
M
Ohta
Kuniyo
K
Inouye
D053493:Cholestanetriol 26-Monooxygenase; D000072467:Cytochrome P450 Family 2; D006801:Humans; D013058:Mass Spectrometry; D008861:Microsomes / Q000378:metabolism*; D015394:Molecular Structure; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D013250:Steroid Hydroxylases / Q000235:genetics / Q000378:metabolism*; D014807:Vitamin D / Q000737:chemistry / Q000378:metabolism*
D011994:Recombinant Proteins; D014807:Vitamin D; D013250:Steroid Hydroxylases; D000072467:Cytochrome P450 Family 2; C506833:CYP2R1 protein, human; C506831:CYP27A1 protein, human; D053493:Cholestanetriol 26-Monooxygenase