[28] Enzymatic deglycosylation of glycoproteins

Deglycosylation of glycoproteins is important in elucidation of structure, function, and biosynthesis of biologically significant glycoproteins. Enzymatic deglycosylation can be brought about by exoglycosidases either used sequentially or in a mixture or by endoglycosidases. The chapter discusses the conditions and the processes of deglycosylation of glycoproteins by exoglycosidases and by endoglycosidases. Denatured glycoproteins are more susceptible to hydrolysis with these enzymes than glycoproteins in their native conformation. Complete deglycosylation of glycoproteins in their native conformation can, however, be achieved by using much higher concentrations of the enzyme. The precise conditions for hydrolysis including enzyme concentration and the incubation time vary with the substrate and, therefore, should be determined for each unknown glycoprotein separately. Despite the discovery of several endoglycosidases that have facilitated the investigations on the structure and biosynthesis of carbohydrates, there still remains a paucity of enzymes with broad specificity that can cleave carbohydrates from glycoproteins in their native forms. There is still a need to continue the efforts to search for new endoenzymes.