Controlling Glycosyltransferase Activity: Inhibition and Enzyme Engineering

Abstract

Glycosyltransferases (GTs) are responsible for the synthesis of a multitude of important glycosylated molecules. These enzymes catalyze the assembly of glycans and glycoconjugates through the transfer of sugar residues from activated donors onto various acceptor molecules. In most cases, the donor molecule consists of a sugar attached to the phosphate group of a nucleotide, but some GTs can use donors consisting of sugars attached to the phosphate groups of other molecules. Transfer of a sugar group from the donor can occur with retention or inversion of the stereochemical configuration of the anomeric center and thus GTs can be classified as either retaining or inverting. GTs have become attractive drug targets due to the important biological roles played by the various glycans that they assemble. Understanding GT structure and function has helped researchers to identify and develop small molecule inhibitors, and the emerging advances in high-throughput screening tools have made feasible the rapid discovery of novel GT inhibitors from diverse compound libraries. Apart from being therapeutic targets, GTs make useful tools as biocatalysts for the production of valuable glycosylated molecules. However, their use in enzymatic synthesis is often limited due to deficiencies in the desired enzyme characteristics. Insights on GT mechanisms and 3D protein structures has permitted structure-guided rational engineering strategies such as site-directed mutagenesis and domain swapping to enhance or modify GT functions. Furthermore, high-throughput GT screening platforms have not only proven to be valuable towards GT engineering by directed evolution, but they are also important tools in exploring the catalytic scope of natural and engineered GTs towards the production of novel glycosides.