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Electronic Journal of Biotechnology

versão On-line ISSN 0717-3458

Resumo

LIN, Ling et al. A novel pH-stable, endoglucanase (JqCel5A) isolated from a salt-lake microorganism, Jonesia quinghaiensis. Electron. J. Biotechnol. [online]. 2016, vol.19, n.6, pp.56-62. ISSN 0717-3458.  http://dx.doi.org/10.1016/j.ejbt.2016.09.004.

Background: Endoglucanase, one of three type cellulases, can randomly cleave internal p-1,4-linkages in cellulose polymers. Thus, it could be applied in agricultural and industrial processes. ResultsA novel endoglucanase gene (JqCel5A) was cloned from Jonesia quinghaiensis and functionally expressed in Escherichia coli Rosetta (DE3). It contained 1722 bp and encoded a 573-residue polypeptide consisting of a catalytic domain of glycoside hydrolase family 5 (GH5) and a type 2 carbohydrate-binding module (CBM2), together with a predicted molecular mass of 61.79 kD. The purified JqCel5A displayed maximum activity at 55°C and pH 7.0, with 21.7 U/mg, 26.19 U/mg and 4.81 U/mg towards the substrate carboxymethyl cellulose, barley glucan and filter paper, respectively. Interestingly, JqCel5A exhibited high pH stability over a broad pH range of pH (3-11), and had good tolerance to a wide variety of deleterious chemicals including heavy metals and detergent. The catalytic mechanism of JqCel5A was also investigated by site mutagenesis and homology-modeling in this study. Conclusions: It was believed that these properties might make JqCel5A to be potentially used in the suitable industrial catalytic condition, which has a broad pH fluctuation and/or chemical disturbance.

Palavras-chave : Protein modeling; Site-directed mutagenesis; Cellulases; Recombinant endoglucanase gene; Catalytic domain ofglycoside hydrolase; Carbohydrate-binding module; High pH stability; Tolerance to deleterious chemicals, Tolerance to heavy metals; Tolerance to detergents.

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