Molecular Identification of Sphingomonas sp. A1 Alginate Lyase (A1-IV') as a Member of Novel Polysaccharide Lyase Family 15 and Implications in Alginate Lyase Evolution(Enzymology, Protein Engineering, and Enzyme Technology)

概要

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Sphingomonas sp. A1 (strain A1) produces three endotypes (A1-I [65 kDa], A1-II [25 kDa], and A1-III [40 kDa]) and an exotype (A1-IV [86 kDa]) alginate lyases in cytoplasm. These four enzymes cooperatively depolymerize alginate into constituent monosaccharides. In addition to the genes for these lyases, novel genes encoding hypothetical proteins homologous with A1-IV were found in the genomes of many bacteria including strain A1. One such protein, A1-IV' (90 kDa) of strain A1, was overexpressed in Escherichia coll cells, purified, and characterized. A1-IV' catalyzed the cleavage of glycosidic bonds in alginate through a β-elimination reaction and released unsaturated di- and trisaccharides as main products, thus indicating that the enzyme is an endotype alginate lyase. A1-IV, which differed from A1-IV in some enzymatic properties, was not expressed in strain A1, suggesting that A1-IV' has no significant role in alginate metabolism. A1-IV' and other A1-IV homologs facilitate the creation of novel polysaccharide lyase family 15 based on their primary structures, implying the evolution route of alginate lyases in family PL-15.
社団法人日本生物工学会の論文
2005-01-25