Analysis of C-3 epimerization in (24R)-24,25-dihydroxyvitamin D3 catalyzed by hydroxysteroid dehydrogenase.

Studies on the C-3 epimerization in (24R)-24,25-dihydroxyvitamin D(3) [24R,25(OH)(2)D(3)] were performed using hydroxysteroid dehydrogenases (HSDs). 3-Epi-24R,25(OH)(2)D(3) was formed from 24R,25(OH)(2)D(3) by the catalysis of 3alpha- or beta-HSD. These HSDs also catalyzed the C-3 epimerization in 3-epi-24R,25(OH)(2)D(3) to form 24R,25(OH)(2)D(3).