DO DE-N-GLYCOSYLATION ENZYMES HAVE AN IMPORTANT ROLE IN PLANT-CELLS

In this review de-N-glycosylation was defined as the removal of the gl ycan(s) from a N-glycosylprotein, by means of enzymes acting on the di -N-acetylchitobiosyl part of the invariant pentasaccharide inner-core of N-glycosylproteins. Peptide-N-4-(N-acetyl-beta-D-glucosaminyl) aspa ragine amidases (PNGase) and endo-N-acetyl-beta-D-glucosaminidases (EN Gase) were both considered as de-N-glycosylation enzymes. A detailed d escription of the characterization and the function of plant PNGases a nd ENGases is presented, together with a brief presentation on the occ urrence and the current knowledge on the function of microbial and ani mal enzymes. De-N-glycosylation of plant glycoproteins was proposed as a possible mechanism for the release of oligosaccharides displaying b iological activities and the removal of N-glycans could also explain t he regulation of protein activity. Each enzyme seems to have a specifi c function during germination and post-germinative development. All th e arguments concur that de-N-glycosylation enzymes have an important r ole in plant cells and confirm that the N-glycosylation/de-N-glycosyla tion system should occur more commonly than presently recognized in li ving organisms.