Cloning, characterization and expression of the chitinase gene of Enterobacter sp. NRG4

A chitinase producing bacterium Enterobacter sp. NRG4, previously isolated in our laboratory, has been reported to have a wide range of applications such as anti-fungal activity, generation of fungal protoplasts and production of chitobiose and N-acetyl D-glucosamine from swollen chitin. In this paper, the gene coding for Enterobacter chitinase has been cloned and expressed in Escherichia coli BL21(DE3). The structural portion of the chitinase gene comprised of 1686 bp. The deduced amino acid sequence of chitinase has high degree of homology (99.0%) with chitinase from Serratia marcescens. The recombinant chitinase was purified to near homogeneity using His-Tag affinity chromatography. The purified recombinant chitinase had a specific activity of 2041.6 U mg(-1). It exhibited similar properties pH and temperature optima of 5.5 and 45°C respectively as that of native chitinase. Using swollen chitin as a substrate, the K(m), k(cat) and catalytic efficiency (k(cat)/K(m)) values of recombinant chitinase were found to be 1.27 mg ml(-1), 0.69 s(-1) and 0.54 s(-1)M(-1) respectively. Like native chitinase, the recombinant chitinase produced medicinally important N-acetyl D-glucosamine and chitobiose from swollen chitin and also inhibited the growth of many fungi.