PEPTIDE-N4-(N-ACETYL-BETA-GLUCOSAMINYL)ASPARAGINE AMIDASE-F CANNOT RELEASE GLYCANS WITH FUCOSE ATTACHED ALPHA-1-]3 TO THE ASPARAGINE-LINKED N-ACETYLGLUCOSAMINE RESIDUE

The ability of peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase F (PNGase F) from Flavobacterium meningosepticum and PNGase A from sweet almonds to deglycosylate N-glycopeptides and N-glycoproteins from plants was compared. Bromelain glycopeptide and horseradish peroxidase-C glycoprotein, which contain xylose linked beta-1 --> 2 to beta-mannose and fucose linked alpha-1 --> 3 to the innermost N-acetylglucosamine, were used as substrates. In contrast to PNGase A, the enzyme from F. meningosepticum did not act upon these substrates even at concentrations 100-fold higher than required for complete deglycosylation of commonly used standard substrates. After removal of alpha-1 --> 3-linked fucose from the plant glycopeptide and glycoprotein by mild acid hydrolysis, they were readily degraded by PNGase F at moderate enzyme concentrations. Hence we conclude that alpha-1 --> 3 fucosylation of the inner N-acetylglucosamine impedes the enzymatic action of PNGase F. Knowledge of this limitation of the deglycosylation potential of PNGase F may turn it from a pitfall into a useful experimental tool.