Characterization, cloning and sequencing of a thermostable endo-(1,3-1,4) beta-glucanase-encoding gene from an alkalophilic Bacillus brevis.

A Bacillus brevis gene coding for an endo-(1,3-1,4)-beta-glucanase was cloned in Escherichia coli and sequenced. The open reading frame contains a sequence of 759 nucleotides encoding a polypeptide of 252 amino acid residues. The amino acid sequence of the beta-glucanase gene showed only a 50% similarity to previously published data for Bacillus endo-(1,3-1,4)-beta-glucanases. The optimum temperature and pH for enzyme activity were 65-70 degrees C and 8-10, respectively. When held at 75 degrees C for 1 h, 75% residual activity was measured. The molecular mass was estimated to be about 29 kDa on sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis and the enzyme was found to be resistant to SDS.