원문정보
초록
영어
From a soil metagenomic plasmid library containing 19,626 clones, we screened for cellulase-positive clones using LB agar plates containing carboxymethyl cellulose. An open reading frame of 1,230 base pairs, which encodes a peptide of 409 amino acid residues, was then identified based on DNA sequencing. The deduced amino acid sequence showed 92% identity with that of lichenase, endo-β-1,3-1,4-glucanase, of Bacillus circulans WL-12 encoded by the bgc gene. This metagenomic lichenase was overexpressed and purified from Escherichia coli C43 (DE3) strain. The purified lichenase showed optimum activity at a pH of 6.0 at 50°C, with Azo-barley-glucan as the substrate. The metal ions Mn2+, Mg2+, Ca2+, and Fe2+ enhanced the enzymatic activity; however, some other metal ions such as Cu2+, and Zn2+, at a concentration of 1 mM, inhibited the enzymatic activity. The Km and Vmax values of the isolated lichenase were determined to be 0.88 mg/ml and 147.2 U/min per mg of protein, respectively. Our results has proven that metagenomics is a powerful tool for isolating novel enzymes with applications in biotechnology. Supported by HTS-based Integrated Technology Development grant.