Glycosyltransferases (GTs) are enzymes that transfer sugars from donor to an acceptor molecule. There are dozens of GT gene families, classified by sequence, sequence motifs and enzymatic function.
GTs are defined by their donor and acceptor specificities and the type of glycosidic linkage they make. For example, a UDP-Gal : ßGal ß1-3 galactosyltransferase transfers galactose from UDP-Gal to a ßGal acceptor residue in a ß1-3 linkage (making a Galß1-3Galß1-R product).
In most eukaryotes there is at least one GT family making each of Galß1-2, Galß1-3, Galß1-4 and Galß1-6 linkages. However, a recent paper in the Journal of Biological Chemistry by Sam Duncan, Rupa Nagar and colleagues in the Ferguson lab breaks this paradigm. Adding to their previous reports, they show now that at least three of these four linkages are made by a single GT gene family, one that would be predicted to be a Galß1-3 GT family.
Mike Ferguson explains: “From this nice work, which also involves some elegant synthetic carbohydrate chemistry from Andrei Nikolaev and colleagues, we can conclude that although trypanosomes lost several GT gene families during their evolution from the “last eukaryotic common ancestor”, they have later compensated for this by evolving one remaining GT family to perform the tasks of the lost families. This is a good, and perhaps the only, example GT convergent evolution.”