First Thermostable Endo-β-1,4-Glucanase from Newly Isolated Xanthomonas sp. EC102

A novel gene encoding thermostable endoglucanase was identified in Xanthomonas sp. EC102 from soil. The gene had 1,458 base pairs of open reading frame, which encode a 52-kDa protein of 486 amino acid residues. Sequence of the amino acid residues was similar with the endoglucanase from Xanthomonas campestris pv. campestris ATCC33913 (GenBank Accession No. NP-638867.1) (94 % identity). The endoglucanase was overexpressed in Escherichia coli BL21 and purified. Temperature for the highest enzymatic activity was 70 °C and pH optima was pH 5.5. The specific activity of the endoglucanase toward carboxymethylcellulose (CMC) was approximately 2 μmol -min^-1 mg^-1, V_max for CMC was 1.44 μmol mg^-1 min^-1, and K_m values was 25.6 mg mL-1. The EC102 endoglucanase was stable at temperatures up to 60 °C, and it was activated by 0.1 mM of Mn²⁺ and Co²⁺. This is the first report about thermostable endoglucanase from Xanthomonas sp.