Abstract
Plants produce a huge number of low molecular weight natural products with diverse structures as well as biological activities. These diversities are occurred by both a wide range of basic structures and multiple modifications of a common skeleton through glycosylation process. Although the glycosyltransferases (UGTs) catalyzing sugar transfer to small molecule aglycones have been extensively characterized, reports on sugar-sugar UGTs that glycosylate the sugar moiety of glycosides are limited.
We have recently cloned a cDNA encoding a novel sugar-sugar UGT (CaUGT3), which catalyzes glucosyl transfer to the 6"-hydroxyl group of the glucose moiety of flavonoid glucoside to form flavonoid gentiobioside, from cultured Catharanthus roseus cells. To gain an insight into the molecular structure governing the acceptor as well as donor specificity of this enzyme, a homology model of CaUGT3 was constructed. The conservation of primary and secondary structure in relation to substrate specificity of CaUGT3 is investigated.
