Glycobiology, 2002, Vol. 12, No. 10 589-597
© 2002 Oxford University Press
Identification and characterization of a Drosophila melanogaster ortholog of human ß1,4-galactosyltransferase VII
Department of Molecular Biology, University of Wyoming, P.O. Box 3944, Laramie, WY 82071-3944, USA
Drosophila melanogaster is widely considered to be an attractive model organism for studying the functions of the carbohydrate moieties of glycoconjugates produced by higher eukaryotes. However, the pathways of glycoconjugate biosynthesis are not as well defined in insects as they are in higher eukaryotes. One way to address this problem is to identify genes in the Drosophila genome that might encode relevant functions, express them, and determine the functions of the gene products by direct biochemical assays. In this study, we used this approach to identify a putative Drosophila ß4-galactosyltransferase gene and determine the enzymatic activity of its product. Biochemical assays demonstrated that this gene product could transfer galactose from UDP-galactose to a ß-xylosyl acceptor, but not to other acceptors in vitro. The apparent Km values for the donor and acceptor substrates indicated that this gene product is a functional galactosyltransferase. Additional assays showed that the enzyme is activated by manganese, has a slightly acidic pH optimum, and is localized in the insect cell Golgi apparatus. These results showed that Drosophila encodes an ortholog of human ß4-galactosyltransferase-VII, also known as galactosyltransferase I, which participates in proteoglycan biosynthesis by transferring the first galactose to xylose in the linkage tetrasaccharide of glycosaminoglycan side chains.
1 Present address: Department of Molecular, Cellular, Developmental Biology and Genetics, Genetic Counseling Program, University of Minnesota, Minneapolis, MN 55455, USA
2 To whom correspondence should be addressed; E-mail: DLJarvis@uwyo.edu
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