Glycosylasparaginase-catalyzed synthesis and hydrolysis of β-aspartyl peptides

Abstract

β-Aspartyl di- and tripeptides are common constituents of mammalian metabolism, but their formation and catabolism are not fully understood. In this study we provide evidence that glycosylasparaginase (aspartyl- glucosaminidase), an N-terminal nucleophile hydrolase involved in the hydrolysis of the N-glycosidic bond in glycoproteins, catalyzes the hydrolysis of β-aspartyl peptides to form L-aspartic acid and amino acids or peptides. The enzyme also effectively catalyzes the synthesis of β-aspartyl peptides by transferring the β-aspartyl moiety from other β-aspartyl peptides or β-aspartylglycosylamine to a variety of amino acids and peptides. Furthermore, the enzyme can use L-asparagine as the β-aspartyl donor in the formation of β-aspartyl peptides. The data show that synthesis and degradation of β-aspartyl peptides are new, significant functions of glycosylasparaginase and suggest that the enzyme could have an important role in the metabolism of β-aspartyl peptides.