Molecular cloning of a Bacillus sp. KK-1 xylanase gene and characterization of the gene product

Abstract

A gene encoding cellulase-free xylanase was cloned from the thermophilic bacterium Bacillus sp. KK-1 into Escherichia coli and the gene product was purified from the recombinant E. coli. This xylanase gene, designated xylY, was composed of 1302 base pairs and encoded a polypeptide of 434 amino acids. No similarity was found between the nucleotide sequence of the xylY gene and those reported for other xylanase genes. The deduced amino acid sequence was homologous to those of cellulases belonging to the β-glycanase family D. The purified enzyme exhibited maximum activity at 55°C but also lost 70% of this activity even after incubation for 30 min at 55°C. Bacillus sp. KK-1 may have acquired the xylY gene by an interspecies gene transfer during adaptation to mesophilic environments.