Endo-beta-1,3-galactanase from winter mushroom Flammulina velutipes |
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Authors: | Kotake Toshihisa Hirata Naohiro Degi Yuta Ishiguro Maki Kitazawa Kiminari Takata Ryohei Ichinose Hitomi Kaneko Satoshi Igarashi Kiyohiko Samejima Masahiro Tsumuraya Yoichi |
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Institution: | Division of Life Science, Graduate School of Science and Engineering, Faculty of Science, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama 338-8570, Japan. kotake@molbiol.saitama-u.ac.jp |
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Abstract: | Arabinogalactan proteins are proteoglycans found on the cell surface and in the cell walls of higher plants. The carbohydrate moieties of most arabinogalactan proteins are composed of β-1,3-galactan main chains and β-1,6-galactan side chains, to which other auxiliary sugars are attached. For the present study, an endo-β-1,3-galactanase, designated FvEn3GAL, was first purified and cloned from winter mushroom Flammulina velutipes. The enzyme specifically hydrolyzed β-1,3-galactan, but did not act on β-1,3-glucan, β-1,3:1,4-glucan, xyloglucan, and agarose. It released various β-1,3-galactooligosaccharides together with Gal from β-1,3-galactohexaose in the early phase of the reaction, demonstrating that it acts on β-1,3-galactan in an endo-fashion. Phylogenetic analysis revealed that FvEn3GAL is member of a novel subgroup distinct from known glycoside hydrolases such as endo-β-1,3-glucanase and endo-β-1,3:1,4-glucanase in glycoside hydrolase family 16. Point mutations replacing the putative catalytic Glu residues conserved for enzymes in this family with Asp abolished activity. These results indicate that FvEn3GAL is a highly specific glycoside hydrolase 16 endo-β-1,3-galactanase. |
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Keywords: | Carbohydrate Cell Wall Enzyme Purification Fungi Hydrolases Arabinogalactan Protein Endo-beta-1 3-Galactanase Glycoside Hydrolase Winter Mushroom Beta-1 3-Galactan |
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