The enzyme, isolated from the plant Withania somnifera (ashwagandha), transfers D-glucose to a beta-hydroxyl group present at the C-27 position in sterols/withanolides, provided the substrate possesses a 17alpha-OH group. Natural substrates are 17alpha-hydroxywithaferin A, 27beta-hydroxywithanone, and 5alpha,6beta,17alpha,27beta-tetrahydroxywithanolide. The enzyme's activity with withanolide A and withanolide U, which lack a 17alpha-hydroxyl group, suggests it may also be able to glucosylate the C-20 beta-OH position, although this has not been verified yet. The enzyme does not glucosylate sterols at the C-3 position.
Madina BR, Sharma LK, Chaturvedi P, Sangwan RS, Tuli R.
Title
Purification and characterization of a novel glucosyltransferase specific to 27beta-hydroxy steroidal lactones from Withania somnifera and its role in stress responses.
