Accepted name: sterol 27-β-glucosyltransferase
Reaction: UDP-α-D-glucose + a 27-hydroxysteroid = UDP + a sterol 27-β-D-glucoside
Systematic name: UDP-α-D-glucose:sterol 27-O-β-D-glucosyltransferase
Comments: The enzyme, isolated from the plant Withania somnifera (ashwagandha), transfers D-glucose to a β-hydroxyl group present at the C-27 position in sterols/withanolides, provided the substrate possesses a 17α-OH group. Natural substrates are 17α-hydroxywithaferin A, 27β-hydroxywithanone, and 5α,6β,17α,27β-tetrahydroxywithanolide. The enzyme's activity with withanolide A and withanolide U, which lack a 17α-hydroxyl group, suggests it may also be able to glucosylate the C-20 β-OH position, although this has not been verified yet. The enzyme does not glucosylate sterols at the C-3 position.
1.  Madina, B.R., Sharma, L.K., Chaturvedi, P., Sangwan, R.S. and Tuli, R. Purification and characterization of a novel glucosyltransferase specific to 27β-hydroxy steroidal lactones from Withania somnifera and its role in stress responses. Biochim. Biophys. Acta 1774 (2007) 1199–1207. [PMID: 17704015]
[EC created 2021]