Endoglucanase, one of three type cellulases, can randomly cleave internal β-1,4-linkages in cellulose
polymers. Thus, it could be applied in agricultural and industrial processes.
A 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.
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.