Enzymatic transglycosylation

The most important functions of carbohydrates are structural roles and energy storage, but carbohydrate parts of glycoproteins and glycolipids are involved in biological functions mainly related to cell recognition events. Carbohydrates are also important molecules in the technological domain. A copious amount of information concerning the synthesis and transformation of complex saccharides in living organisms exists nowadays: the enzymes responsible for the synthesis of glycosidic linkage have been recognized as glycosyltransferases. Glycoside hydrolases (glycosidases) are different enzymes responsible for the hydrolysis of glycosidic linkages, but they can be efficiently used in synthesis. Indeed, at the present time, genetic engineering of glycosidases has emerged as a powerful tool for scientists, in the synthetic field, with the aim to set up chemically, efficient biocatalysts. In this contribution, the glycosyl transfer between oxygen nucleophiles will be analyzed from the chemical and the biotechnological points of view. Chemical machinery for hydrolysis and synthesis of the enzyme glycoside hydrolases and glycosyltransferases will be analyzed, including issues inherent to donors and acceptors and biocatalyst natural sources; in particular, discussing the modern genetic efforts to prepare tailored enzymes with high synthetic ability. Case studies for laboratory and industrial importance are analyzed as well.