Abstract
Glycoside hydrolases and glycosyltransferases are widespread groups of carbohydrate-active enzymes present in virtually all organisms and are involved, respectively, in the hydrolysis and in the biosynthesis of glycosidic bonds between carbohydrates or between a carbohydrate and a noncarbohydrate moiety. The wide diversity of carbohydrate structures is accompanied by an equal diversity of the enzymes responsible for both their synthesis and selective hydrolysis. Carbohydrate-active enzymes have long been classified according to their substrate specificity, which formed the basis of their Enzyme Commission (EC number) classification by the IUBMB. Classifications of these and other classes of carbohydrate-active enzymes, like polysaccharide lyases and carbohydrate esterases, can be used to understand the carbohydrate flux in organisms made possible by the advent of genomics. This universal system can be used for the identification and classification of glycoside hydrolases and glycosyltransferases from hyperthermophiles.