Abstract
Enzymes that catalyse the synthesis and breakdown of glycosidic bonds account for 1–3% of the proteins encoded by the genomes of most organisms. At the current rate, over 12 000 glycosyltransferase and glycoside hydrolase open reading frames will appear during 2006. Recent advances in the study of the structure and mechanism of these carbohydrate-active enzymes reveal that glycoside hydrolases continue to display a wide variety of scaffolds, whereas nucleotide-sugar-dependent glycosyltransferases tend to be grafted onto just two protein folds. The past two years have seen significant advances, including the discovery of a novel NAD
+-dependent glycosidase mechanism, the dissection of the reaction coordinate of sialidases and a better understanding of the expanding roles of auxiliary carbohydrate-binding domains.