Lectin-based structural glycomics: a practical approach to complex glycans

Glycans exist in nature in various forms of glycoconjugates, i.e., glycoproteins, glycolipids, and glycosaminoglycans, either in soluble or membrane-bound forms. One of their prominent properties distinguished from nucleic acids and proteins is "heterogeneity" largely attributed to their inherent features of biosynthesis. In general, various methods based on the physicochemical principles have been taken for their separation and structural determination although all of them require prior liberation of glycans and appropriate labeling. On the other hand, a series of carbohydrate-binding proteins, or "lectins," have extensively been used in a more direct manner for cell typing, histochemical staining, and glycoprotein fractionation. Although most procedures conventionally used are useful, unfortunately they lack "throughput" comparable to a performance required for current omics studies. Recently, a novel technique called lectin microarray has attracted increasing attention from not only glycoscientists but also researchers in other fields, because it is straightforward and also informative. The method is innovating in that it enables direct approach to glycoconjugates such as glycoproteins and even cells without liberation of glycans from the core substrate, and therefore can be effectively applied for the sake of differential profiling in various fields. Concept, strategy, and technical advancement of lectin microarray are described. Also, as an introduction to glycomics, the authors explain the motivation to challenge this theme.