25-hydroxyvitamin D-1 alpha hydroxylase, mitochondrial

Definition:

A cytochrome P450 monooxygenase involved in vitamin D metabolism and in calcium and phosphorus homeostasis. Catalyzes the rate-limiting step in the activation of vitamin D in the kidney, namely the hydroxylation of 25-hydroxyvitamin D3/calcidiol at the C1alpha-position to form the hormonally active form of vitamin D3, 1alpha,25-dihydroxyvitamin D3/calcitriol that acts via the vitamin D receptor (VDR). Has 1alpha-hydroxylase activity on vitamin D intermediates of the CYP24A1-mediated inactivation pathway. Converts 24R,25-dihydroxyvitamin D3/secalciferol to 1-alpha,24,25-trihydroxyvitamin D3, an active ligand of VDR. Also active on 25-hydroxyvitamin D2. Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, and reducing the second into a water molecule, with two electrons provided by NADPH via FDXR/adrenodoxin reductase and FDX1/adrenodoxin.

References:

[1]. Edith K Y Tang, et al. Expression of human CYP27B1 in Escherichia coli and characterization in phospholipid vesicles. FEBS J. 2012 Oct;279(19):3749-3761. [Content Brief]

[2]. Xuemei Wang, et al. Novel gene mutations in patients with 1alpha-hydroxylase deficiency that confer partial enzyme activity in vitro. J Clin Endocrinol Metab. 2002 Jun;87(6):2424-30. [Content Brief]

[3]. S Kitanaka, et al. Inactivating mutations in the 25-hydroxyvitamin D3 1alpha-hydroxylase gene in patients with pseudovitamin D-deficiency rickets. N Engl J Med. 1998 Mar 5;338(10):653-61. [Content Brief]

[4]. N Sawada, et al. Enzymatic properties of human 25-hydroxyvitamin D3 1alpha-hydroxylase coexpression with adrenodoxin and NADPH-adrenodoxin reductase in Escherichia coli. Eur J Biochem. 1999 Nov;265(3):950-6. [Content Brief]

[5]. S Kitanaka, et al. No enzyme activity of 25-hydroxyvitamin D3 1alpha-hydroxylase gene product in pseudovitamin D deficiency rickets, including that with mild clinical manifestation. J Clin Endocrinol Metab. 1999 Nov;84(11):4111-7. [Content Brief]

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