A chitinase gene from Serratia marcescens was cloned and expressed in Escherichia coli and the properties of recombinant chitinase rCHI-2 were characterized. The optimum catalytic pH of rCHI-2 was 6.0. It was stable in the pH range of 6.0-9.0 and could maintain more than 90% of its relative enzyme activity after incubation at 37 °C for 1 h. The optimum catalytic temperature of the enzyme was 55 °C and 85% of enzyme activity was remained after incubation at 45 °C for 1 h. The activation energy of the thermal inactivation of the enzyme was 10.9 kJ/mol and the Michaelis-Menten constant was 3.2 g/L. The purified rCHI-2 was found to be highly stable at 45 °C with half-life (t1/2) of 289 min and thermodynamic parameters ΔH*, ΔG* and ΔS* revealed high affinity of rCHI-2 for chitin. Hg2+ was found to be able to inhibit the enzyme activity reversibly, while IC50 and inhibition constant of Hg2+ on the enzyme were 34.8 μmol/L and 44.6 μmol/L, respectively. Moreover, rCHI-2 could specifically hydrolyze colloidal chitin into GlcNAc2 as the major product.

中文翻译：

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粘质沙雷氏菌的几丁质酶的表达和表征。

克隆了粘质沙雷氏菌的几丁质酶基因并在大肠杆菌中表达，表征了重组几丁质酶rCHI-2的特性。rCHI-2的最佳催化pH为6.0。它在6.0-9.0的pH范围内稳定，并且在37°C孵育1小时后可以保持90％以上的相对酶活性。该酶的最佳催化温度为55°C，在45°C孵育1小时后，仍保留了85％的酶活性。酶热失活的活化能为10.9 kJ / mol，Michaelis-Menten常数为3.2 g / L。发现纯化的rCHI-2在45°C时高度稳定，半衰期（t1 / 2）为289分钟，并且热力学参数ΔH*，ΔG*和ΔS*显示rCHI-2对几丁质具有高度亲和力。发现Hg2 +能够可逆地抑制酶的活性，Hg2 +对酶的IC50和抑制常数分别为34.8μmol/ L和44.6μmol/ L。此外，rCHI-2可以特异性地将胶体几丁质水解为主要产物GlcNAc2。