Vitamin D 1 alpha-hydroxylase.

The rate-limiting, hormonally regulated step in the bioactivation of vitamin D is renal 1 alpha-hydroxylation by P450c1 alpha. In late 1997, we reported the cloning of the human cDNA and gene from keratinocytes, and established that P450c1 alpha mutations cause vitamin D-dependent rickets, type I, while three other groups reported the cloning of the rodent enzyme. The genetics of P450c1 alpha are well established, with studies of over 30 patients, but the molecular mechanisms for the hormonal regulation of P450c1 alpha are still under investigation.