Enzymatic synthesis of the N-glycosidic bond by beta-aspartylation of glycosylamines.

Glycosylasparaginase (EC 3.5.1.26) is an amidase, which cleaves the N-glycosidic linkage during glycoprotein degradation leading to the liberation of L-aspartic acid from various glycoasparagines. In this work we demonstrate that glycosylasparaginase is also capable of catalyzing the synthesis of the N-glycosidic bond by N-beta-aspartylation of beta-glycosylamine using 1-amino-N-acetylglucosamine as the nucleophile and L-aspartic acid beta-methyl ester as the beta-aspartyl donor. Kinetic studies indicated that beta-glycosylamine has 1390-fold higher reactivity than water in the de-beta-aspartylation of the beta-aspartylenzyme, indicative of the presence of a beta-glycosylamine binding sub-site at the substrate binding site of glycosylasparaginase. The reaction can be applied to glycosylaparaginase-catalyzed biosynthesis of novel glycoasparagines.