Do de-N-glycosylation enzymes have an important role in plant cells?

Abstract

In this review de-N-glycosylation was defined as the removal of the glycan(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-N4-(N-acetyl-beta-D-glucosaminyl) asparagine amidases (PNGase) and endo-N-acetyl-beta-D-glucosaminidases (ENGase) were both considered as de-N-glycosylation enzymes. A detailed description of the characterization and the function of plant PNGases and ENGases is presented, together with a brief presentation on the occurrence and the current knowledge on the function of microbial and animal enzymes. De-N-glycosylation of plant glycoproteins was proposed as a possible mechanism for the release of oligosaccharides displaying biological activities and the removal of N-glycans could also explain the regulation of protein activity. Each enzyme seems to have a specific function during germination and post-germinative development. All the arguments concur that de-N-glycosylation enzymes have an important role in plant cells and confirm that the N-glycosylation/de-N-glycosylation system should occur more commonly than presently recognized in living organisms.