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.
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The expected taxonomic range for this enzyme is: Withania somnifera
UDP-alpha-D-glucose + a 27-hydroxysteroid = UDP + a sterol 27-beta-D-glucoside
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UDP-alpha-D-glucose + a 27-hydroxysteroid = UDP + a sterol 27-beta-D-glucoside
enzyme transferes beta-D-glucose to beta-OH present at C-20, C-21 and C-27 positions in sterols/withanolides, provided the sterol posesses a 17beta-OH group. Does not glycosylate sterols at the C-3 position
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.
can conjugate glucose to C-27 position in the withanolide lactone ring and to higher positions in sterols using UDP-glucose as glucose donor, activity is enhanced following the application of salicylic acid and decreased rapidly on exposure of the plants to heat shock, suggesting a functional role of the enzyme in biotic and abiotic stresses
can conjugate glucose to C-27 position in the withanolide lactone ring and to higher positions in sterols using UDP-glucose as glucose donor, activity is enhanced following the application of salicylic acid and decreased rapidly on exposure of the plants to heat shock, suggesting a functional role of the enzyme in biotic and abiotic stresses
enzyme exhibits broad sterol specificity by glucosylating a variety of sterols/withanolides with beta-OH group at C-17, C-21 and C-27 positions. It transfers glucose to the alkanol at C-25 position of the lactone ring, provided an alpha-OH is present at C-17 in the sterol skeleton. It follows an ordered sequential bisubstrate reaction mechanism, in which UDP-glucose and sterol are the first and second binding substrates. The enzyme does not glucosylate sterols at the C-3 position
Madina, B.R.; Sharma, L.K.; Chaturvedi, P.; Sangwan, R.S.; Tuli, R.
Purification and characterization of a novel glucosyltransferase specific to 27beta-hydroxy steroidal lactones from Withania somnifera and its role in stress responses
Madina, B.; Sharma, L.; Chaturvedi, P.; Sangwan, R.; Tuli, R.
Purification and characterization of a novel glucosyltransferase specific to 27beta-hydroxy steroidal lactones from Withania somnifera and its role in stress responses
2.4.1.385 sterol 27-beta-glucosyltransferase
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