Biological roles of oligosaccharides: all of the theories are correct

By A. Varki. 1993

Abstract Many different theories have been advanced concerning the biological roles of the oligosaccharide units of individual classes of glycoconjugates. Analysis of the evidence indicates that while all of these theories are correct, exceptions to each can also be found. The biological roles of oligosaccharides appear to span the spectrum from those that are trivial, to those that are crucial for the development, growth, function or survival of an organism. Some general principles emerge. First, it is difficult to predict a priori the functions a given oligosaccharide on a given glycoconjugate might be mediating, or their relative importance to the organism. Second, the same oligosaccharide sequence may mediate different functions at different locations within the same organism, or at different times in its ontogeny or life cycle. Third, the more specific and crucial biological roles of oligosaccharides are often mediated by unusual oligosaccharide sequences, unusual presentations of common terminal sequences, or by further modifications of the sugars themselves. However, such oligosaccharide sequences are also more likely to be targets for recognition by pathogenic toxins and microorganisms. As such, they are subject to more intra- and inter-species variation because of ongoing host—pathogen interactions during evolution. In the final analysis, the only common features of the varied functions of oligosaccharides are that they either mediate ‘specific recognition’ events or that they provide ‘modulation’ of biological processes. In so doing, they generate much of the functional diversity required for the development and differentiation of complex organisms, and for their interactions with other organisms in the environment.

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Citations in the corpus

Biological roles of glycans (2016, background): “The alpha(1,3)Fucosyltransferase Fuc-TVII controls leukocyte trafficking”
Posttranslational Protein Modification in Archaea (2005, background): “In Eucarya, the glycan moieties of glycosylated proteins fulfill a multitude of roles related to protein solubility, folding, stability and turnover, and subcellular localization as well as participating in numerous recognition events (46, 157, 333, 409, 448).”
N-linked protein glycosylation in the ER. (2013, background): “In addition, N-glycosylation is much more frequent in multicellular than in unicellular species [98], supporting the hypothesis that diversifying glycosylation plays a major role in the evolution of multicellularity [99].”
Sialic acids in the brain: gangliosides and polysialic acid in nervous system development, stability, disease, and regeneration. (2014, background): “Cell surface glycans modulate cell functions by several distinct mechanisms (508).”
Prediction, conservation analysis, and structural characterization of mammalian mucin-type O-glycosylation sites. (2005, background): “…protein-bound glycans: specific carbohydrate epitopes can serve as ligands for receptors that mediate recognition events or glycan structures can be employed to change the biophysical properties of a protein, such as charge, solubility, folding, or sensitivity toward proteases (Varki, 1993).”
Identification and Quantification of Protein Glycosylation (2012, background): “The two major types of glycosylation, N-linked and O-linked, are both involved in the maintenance of protein conformation and activity, in protein protection from proteolytic degradation, and in protein intracellular trafficking and secretion [1].”
Protein glycosylation: nature, distribution, enzymatic formation, and disease implications of glycopeptide bonds. (2002, background): “The β-glycosylamine linkage of GlcNAc to Asn represents the most widely distributed carbohydrate–peptide bond and is the site of attachment for a large variety of complex and polymannose oligosaccharides (Spiro, 1973; Montreuil, 1980) in proteins with demonstrated biological importance (Varki, 1993)”
Mutations in the O-mannosyltransferase gene POMT1 give rise to the severe neuronal migration disorder Walker-Warburg syndrome. (2002, background): “Family 4 is a Gypsy family from Italy and has been described elsewhere (Villanova et al. 1998).”