Enzymatic polymerization to novel polysaccharides having a glucose-N-acetylglucosamine repeating unit, a cellulose-chitin hybrid polysaccharide |
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Authors: | Kobayashi Shiro Makino Akira Matsumoto Hironori Kunii Shigeru Ohmae Masashi Kiyosada Toshitsugu Makiguchi Ken Matsumoto Akira Horie Michinobu Shoda Shin-Ichiro |
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Institution: | Department of Materials Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan. kobayash@kit.ac.jp |
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Abstract: | A cellulose-chitin hybrid polysaccharide having alternatingly beta(1-->4)-linked D-glucose (Glc) and N-acetyl-d-glucosamine (GlcNAc) was synthesized via two modes of enzymatic polymerization. First, a sugar oxazoline monomer of Glcbeta(1-->4)GlcNAc (1) was designed as a transition-state analogue substrate (TSAS) monomer for chitinase catalysis. Monomer 1 was recognized by chitinase from Bacillus sp., giving rise to a cellulose-chitin hybrid polysaccharide (2) via ring-opening polyaddition with perfect regioselectivity and stereochemistry. Molecular weight (M(n)) of 2 reached 4030, which corresponds to 22 saccharide units. Second, a sugar fluoride monomer of GlcNAcbeta(1-->4)Glc (3) was synthesized for the catalysis of cellulase from Trichoderma viride. The enzyme catalyzed polycondensation of 3, providing a cellulose-chitin hybrid polysaccharide (4) in regio- and stereoselective manner. M(n) of 4 reached 2840, which corresponds to 16 saccharide units. X-ray diffraction measurements revealed that these hybrid polysaccharides did not form any characteristic crystalline structures. Furthermore, these unnatural hybrids of 2 and 4 were successfully digested by lysozyme from human neutrophils. |
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