Vol.5 No.3 2012

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Research paper : Development of basic tools for glycoscience and their application to cancer diagnosis (H. Narimatsu)−204−Synthesiology - English edition Vol.5 No.3 (2012) the first step.(2) Synthesis:Glycosyltransferases were expressed as recombinant enzymes based on the obtained glycogenes, and used in combination to synthesize glycans with a variety of structures to make a glycan library. Biochemical synthesis of glycans requires a huge amount of work and time. Moreover, an innovative organic chemical synthesis method for glycans has not yet been developed, and synthesis with organic solvents is environmentally offensive. Synthesis of complicated glycans with a variety of structures is impossible, and it takes considerable time to create even one kind of structure. The only advantage is that once an organic chemical synthesis method is established, mass production at an industrial level would become possible. In contrast, the glycogenes that were comprehensively obtained at the previous step were expressed as recombinant enzymes for enzymological synthesis of glycans. Through the combination of a variety of enzymes, quite a lot of desired glycans in a variety of structures could be synthesized freely in a short time. Glycosyltransferases are highly substrate-specific, and thus one kind of enzyme can synthesize only one kind of structure. Therefore, certain glycan structures are synthesized easily and rapidly by the glycosyltransferases with known substrate-specificity. The reaction is hydrolytic and thus is eco-friendly. The disadvantage is that because the enzymes are derived from human origins, they are extremely unstable and the production costs much. However, it is impossible to use glycosyltransferases obtained from lower organisms alternatively for synthesis of human glycan structures. Therefore, the enzyme method is very suitable for synthesis of a small amount of variable glycans, but not for mass production.(3) Structures:In the Structural Glycomics (SG) Project, the above-obtained glycans with elucidated structures were used as the standards and contributed to the development of glycan analysis technologies. This enzyme method is suitable to produce a few milligrams of many kinds of glycans required as the standard substances. We thus established two structure elucidation methods using the standard glycans and glycoproteins: Tandem mass spectrometry (MSn method) and lectin array method. Each of them has advantages and disadvantages, and is suitable for different purposes. The MSn method is superior in the following: (1) The analysis is easy for everyone. (2) The glycan structure can be determined. It is inferior in the following: (1) The analysis requires relatively large amounts of glycans (about several micrograms). (2) The glycans must be purified prior to analysis. On the other hand, the lectin array is superior in the following: (1) The sensitivity is very high. (2) The antibody-overlay method does not require complete purification of the target glycoproteins. (3) Comparison of glycan profiling among multiple samples is possible. Fig. 2 The three main themes of glycoscienceGlycogene (GG) Project: Establishment of glycogene library, Structural Glycomics (SG) Project: Glycan engineering (structural analysis technologies), Medical Glycomics (MG) Project: Application of determined functions (functions and biomarkers)Industrial application Medical application (New diagnostic systems, biomarkers…)Synthesized glycans (Functional oligosaccharide)Modified glycoproteins (Pharmaceuticals) …Promotion for industrial and medical applications(Glycoprotein formulations, quality control of stem cells…)FunctionsFunctionsBiomarkers[MG Project]CreationFormsFunctions of useful glycansDisease model systemsSynthesisStructure[GG Project][SG Project]Application of synthesizedglycansStructural information of functional molecules[SG Project]KO/Tg models (modified glycans)KO/Tg modelsEnzymesGlycogenesEnzymes[GG Project]Structural information of useful glycansStructural analysis

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