Vitamin D hydroxylases

✍ Scribed by Helen L. Henry

• Book ID: 102878661
• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 510 KB
• Volume: 49
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.240490103

✦ Synopsis

Abstract

There are three mixed function oxidases which catalyze hydroxylations of vitamin D and its derivatives. These include the hepatic mitochondrial or microsomal vitamin D~3~‐25‐hydroxylase and the two renal mitochondrial enzymes which further hydroxylate 25‐hydroxyvitamin‐D~3~ (25‐OH‐D~3~) to form 24R,25‐dihydroxyvitamin D~3~ (24,25(OH)~2~D~3~) and 1,25‐dihydroxyvitamin D~3~ [1,25(OH)~2~D~3~], the primary steroid hormonal derivative of vitamin D~3~. All three enzymes are cytochrome P450 dependent. The two renal mitochondrial enzymes are regulated, usually in a reciprocal fashion. The intracellular signalling systems involved in this regulation include 1,25(OH)~2~D~3~ itself and both protein kinases A and C. Recent progress has been made in the purification and cloning of the vitamin D~3~‐25‐hydroxylase and the 25‐OH‐D~3~‐24‐hydroxylase. When the 25‐OH‐D~3~‐1‐hydroxylase is purified and cloned, efforts which have thus far been frustrated by its low abundance, fertile new ground for the study of the regulation of vitamin D metabolism at the molecular level will be opened up.