| Abstract: | O-Glycosyltransferase(s) extracted from apple (Malus pumila Mill) fruit skin showed activity towards a range of flavonols and anthocyanins. However, no glycosylating activity was shown towards a dihyroflavonol (dihydroquercetin), a flavanone (eriodictyol) or a flavone (luteolin). The enzyme preparation glycosylated those flavonoids normally present in apple skins (quercetin and cyanidin) and in addition several other related compounds (delphinidin, fisetin, isorhamnetin, kaempferol, myricetin and pelargonidin). This enzyme(s) specifically transferred the glycosyl moiety from sugar nucleotide donors to the 3-position of the flavonoid nucleus. Only flavonoid 3-glycosides occur naturally in apple skin. Activity with different sugar donors was in the order galactose>glucose>xylose, which reflected the ratios of cyanidin and quercetin glycosides found in apple fruit skin. There were slight differences in the relative UFGT activity with quercetin and the three different sugar donors between ‘Granny Smith’ and ‘Splendour’, and this was reflected by similar differences in the ratios of endogenous quercetin glycosides. ©1997 SCI |
