Cloning and expression of the Bacillus circulans endo-β-1,3-1,4-glucanase gene (bglBC1) in Escherichia coli

A gene coding for the endo-beta-1,3-1,4-glucanase of B. circulans ATCC21367 was cloned into Escherichia coli. The cloned enzyme hydrolyzed lichenan or barley beta-glucan to produce 3-O-beta-cellobiosyl-d-glucose as a main product but was inactive with carboxymethyl cellulose, laminarin and xylan. The enzyme, M-r=28 kDa, remained within the cytoplasm of E. coli. A 771 bp open reading frame was in the 2 kb PstI fragment of the recombinant plasmid pLL200K. The deduced protein sequence consists of 257 amino acids and has a putative signal peptide of 26 amino acids. The amino acid sequence of the endo-beta-1,3-1,4-glucanase showed 68 and 51% homology to previously reported endo-beta-1,3-1,4-glucanases from Bacillus strain N-137 and B. brevis, respectively.