Endo-N-Acetyl-β-D-Glucosaminidases and Peptide-N4-(N-acetyl-β-D-Glucosaminyl) Asparagine Amidases: More Than Just Tools

Abstract

Since the discovery of endo-N-acetyl-β-D-glucosaminidases (ENGase) and peptide-N4-(N-acetyl-β-D-glucosaminyl) asparagine amidases (PNGase) most of the published work described their use for structural studies. Less attention was given to the potential roles of those enzymes in the physiology of the cells/organisms they produced them. The scope of this review is firstly to analyse the data on the occurrence and characteristics of murein-, chitin-, and N-glycan-ENGases acting on GlcNAc-containing polymers in three structural families, namely murein, chitin, and N-glycosylproteins, and of PNGases, only acting on N-glycosylproteins, and secondly to discuss the biological roles of the enzymes in the producing cells. The analysis demonstrates the remarkable diversity of the enzymes, and simultaneously the interest of studying their substrate specificity and their structural features. Many examples illustrate the importance of the structure/function relationships studies. Diverse biological roles were anticipated, e.g. they are useful for feeding purposes, are implicated in pathogenesis processes, modulate the activity of macromolecules, and help in the destruction of misfolded proteins. Their effect can be direct or indirect, through the reaction products. Current knowledge only partially explains the biological roles of ENGases and PNGases, thus further studies are expected for determining novel possibilities and elucidating other cell pathways.