Endoglucanase S, a novel endocellulase exhibiting exoglucanase activity from a newly isolated Streptomyces sp. LX

Abstract

A novel endocellulase, designated as endoglucanase S, was purified to homogeneity from culture supernatant fluids of the newly isolated Streptomyces sp. LX, and shown not to be identical with previously described endo-β-1,4-glucanases. Both endo- and exo-cellulase activities were found to reside on a monomeric protein of 48 kDa. Its temperature optimum is 50 °C, and it was stable at 60 °C. The optimum pH is 5·5, and it has a broad pH stability from pH 3·0–7·0. The action of the enzyme on carboxymethylcellulose (CMC) suggested that the enzyme behaved as endoglucanase, whereas it was also active on crystalline cellulose with cellodextrin as end-product. Fragmentation of filter paper revealed that the degree of polymerization of residual cellulose decreased with time but only 5·2% of filter paper was converted into soluble carbohydrate.