MOLECULAR-CLONING OF CDNA AND GENOMIC DNA FOR HUMAN 25-HYDROXYVITAMIND-3 1-ALPHA-HYDROXYLASE

The 25-hydroxyvitamin D-3 1 alpha-hydroxylase (1 alpha-hydroxylase) is a cytochrome P450 enzyme that catalyzes the conversion of 25-hydroxyv itamin D-2 to 1 alpha,25-dihydroxyvitamin D-3. This enzyme plays an im portant role in calcium homeostasis. Here we report the molecular clon ing of cDNA and gene for human 1 alpha-hydroxylase. The cDNA clone was obtained from a human kidney cDNA library by cross-hybridization with a previously cloned rat cDNA probe. The cDNA consists of 2469 bp and encodes a protein of 508 amino acids that shows 82.5% sequence identit y with the rat enzyme. A computer-aided homology search revealed that 1 alpha-hydroxylase shares a relatively high homology with vitamin D-3 25-hydroxylase (about 40% amino acid identity). Northern blot analysi s showed that the 2.5-kb mRNA is most abundant in kidney, The gene for human 1 alpha-hydroxylase spans approximately 6 kb, is composed of ni ne exons, and is present as a single copy. This molecular cloning make s it possible to investigate the genetic mechanism of diseases related to calcium metabolism, including vitamin D-dependency rickets type I. (C) 1997 Academic Press.