Lysosomal degradation of Asn‐linked glycoproteins

The FASEB JournalVolume 3, Issue 14 p. 2615-2622 ReviewsFree to Read Lysosomal degradation of Asn-linked glycoproteins Nathan N. Aronson Jr., Nathan N. Aronson Jr. Department of Molecular and Cell Biology, The Pennsylvania State University, University Park, Pennsylvania, 16802 USASearch for more papers by this authorMichael J. Kuranda, Michael J. Kuranda Department of Molecular and Cell Biology, The Pennsylvania State University, University Park, Pennsylvania, 16802 USASearch for more papers by this author Nathan N. Aronson Jr., Nathan N. Aronson Jr. Department of Molecular and Cell Biology, The Pennsylvania State University, University Park, Pennsylvania, 16802 USASearch for more papers by this authorMichael J. Kuranda, Michael J. Kuranda Department of Molecular and Cell Biology, The Pennsylvania State University, University Park, Pennsylvania, 16802 USASearch for more papers by this author First published: 01 December 1989 https://doi.org/10.1096/fasebj.3.14.2531691Citations: 86AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Abstract Catabolism of Asn-linked glycoproteins to monosaccharides and amino acids occurs in lysosomes. Breakdown must be complete to avoid lysosomal storage diseases that occur when fragments as small as dimers are left undigested. Recent results have clarified several aspects of Asn-linked glycoprotein catabolism in mammals. First, degradation of the oligosaccharide portion is accomplished by exo-glycosidases, which act only from the nonreducing end of chains to release sugar monomers as products. In contrast, proteolysis can proceed from both end and internal points along the polypeptide to eventually yield free amino acids. A second important feature of the glycoprotein disassembly pathway is that the hydrolytic steps can be grouped into two sets of ordered reactions: I) stepwise hydrolysis of the major portion of the oligosaccharide chains by a set of exoglycosidases, and II) ordered disassembly of the protein and the oligosaccharide-to-protein linkage region. Process II can vary at a single reaction step depending on the species in which degradation takes place. Thus, the last step of reaction sequence II can be either: 1) hydrolysis of the actual peptide-to-carbohydrate linkage, or 2) removal of the reducing-end GlcNAc from a previously freed oligosaccharide. The latter cleavage is catalyzed by the lysosomal glycosidase chitobiase. Chitobiase has been found only in humans and rats and not in other mammals (dogs, cats, goats, sheep, cats, or cattle). The hydrolytic mechanism of this enzyme is unique as it appears to be a reducing-end glycosidase and can be viewed as an accessory step in the human and rat digestive pathways. The species that lack this enzyme likely rely on exo-β-d-glucosaminidase to cleave GlcNAc from both outer chain residues and the chitobiose moiety at the protein-to-carbohydrate linkage.—Aronson, N. N., Jr.; Kuranda, M. J. Lysosomal degradation of Asn-linked glycoproteins. FASEB J. 3: 2615-2622; 1989. Citing Literature Volume3, Issue14December 1989Pages 2615-2622 RelatedInformation