Flavonol-3-O-glycoside xylosyltransferase () is an enzyme that catalyzes the general chemical reaction
UDP-D-xylose + a flavonol 3-O-glycoside UDP + a flavonol 3-[-D-xylosyl-(1->2)-beta-D-glycoside]
The two substrates of this enzyme characterised from tulip and Euonymus alatus are a flavonol 3-O-glycoside and UDP-D-xylose. The enzyme transfers the xylose sugar unit to give the corresponding flavonol 3-[-D-xylosyl-(1->2)-beta-D-glycoside, with uridine diphosphate (UDP) as a byproduct.
For example, rutin is converted to quercetin 3-(2G-xylosylrutinoside):
The enzyme is a glycosyltransferase, specifically a pentosyltransferases. The systematic name of this enzyme class is UDP-D-xylose:flavonol-3-O-glycoside 2''-O-beta-D-xylosyltransferase.
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