Novel Chitosanase from Streptomyces griseus HUT 6037 with Transglycosylation Activity(Biochemistry & Molecular Biology)

概要

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Streptomyces griseus HUT 6037 inducibly produced two chitosanases when grown on chitosan. To elucidate the mechanism of degradation of chitinous compound by this strain, chitosanases I and II of S. griseus HUT 6037 were purified and characterized. The purified enzymes had a molecular mass of 34 kDa. Their optimum pH was 5.7, and their optimum temperature was 60℃. They hydrolyzed not only partially deacetylated chitosan, but also carboxymethylcellulose. Time-dependent ^1H-NMR spectra showing hydrolysis of (GlcN)_6 by the chitosanases were obtained for identification of the anomeric form of the reaction products. Both chitosanases produced the β-form specifically, indicating that they were retaining enzymes. These enzymes catalyzed a glycosyltransfer reaction in the hydrolysis of chitooligosaccharides. The N-terminal and internal amino acid sequences of chitosanase II were identified. A PCR fragment corresponding to these amino acid sequences was used to screen a genomic library for the entire gene encoding chitosanase II. Sequencing of the choII gene showed an open reading frame encoding a protein with 359 amino acid residues. The deduced primary structure was similar to endoglucanase E-5 of Thermomonospora fusca, which enzyme belongs to family 5 of the glycosyl hydrolases. This is the first report of a family 5 chitosanase with transglycosylation activity.
社団法人日本農芸化学会の論文
2003-02-23