Journal Article

Functional and Structural Characterization of a Flavonoid Glucoside 1,6-Glucosyltransferase from <i>Catharanthus roseus</i>

Sayaka Masada, Kazuyoshi Terasaka, Yukie Oguchi, Seiji Okazaki, Tunehiro Mizushima and Hajime Mizukami

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 50, issue 8, pages 1401-1415
Published in print August 2009 | ISSN: 0032-0781
Published online June 2009 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcp088
Functional and Structural Characterization of a Flavonoid Glucoside 1,6-Glucosyltransferase from Catharanthus roseus

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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Sugar–sugar glycosyltransferases play an important role in structural diversity of small molecule glycosides in higher plants. We isolated a cDNA clone encoding a sugar–sugar glucosyltransferase (CaUGT3) catalyzing 1,6-glucosylation of flavonol and flavone glucosides for the first time from Catharanthus roseus. CaUGT3 exhibited a unique glucosyl chain elongation activity forming not only gentiobioside but also gentiotrioside and gentiotetroside in a sequential manner. We investigated the functional properties of CaUGT3 using homology modeling and site-directed mutagenesis, and identified amino acids positioned in the acceptor-binding pocket as crucial for providing enough space to accommodate flavonoid glucosides instead of flavonoid aglycones. These results provide basic information for understanding and engineering the catalytic functions of sugar–sugar glycosyltransferases involved in biosynthesis of plant glycosides.

Keywords: Catharanthus roseus; Flavonoid glucoside 1,6-glucosyltransferase; Functional characterization; Homology modeling; Sugar–sugar glycosyltransferase

Journal Article.  6435 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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