Cloning and Characterization of the Gene Encoding a Novel β-Galactosidase from Bacillus circulans

Abstract

A novel β-galactosidase (β-gal) gene was cloned from Bacillus circulans ATCC 31382. The coding region was 1, 758 bp and encoded a polypeptide of 586 amino acids with a deduced molecular mass of 66, 888. Active staining for β-gal showed that B. circulans ATCC 31382 produced three β-gal isozymes. Two of these were detected in Biolacta N5 (Daiwakasei Co.), but the product of this novel gene corresponded to the one not contained in Biolacta N5. The novel β-gal showed the highest amino acid sequence identity (43.3% ) with a β1→3 > 1→4 galactosidase from Xanthomonas manihotis and was also highly similar to β-gals from animals, plants, and fungi. This suggests an evolutionary relationship between this novel gene and those of eukaryotic origins. One of the two B. circulans β-gals, the nucleotide sequences of which are available in the GenBank, was 20% identical to the novel β-gal. Other bacterial β-gals showed little or no similarity. We propose that this novel β-gal be called B. circulans β-gal-3, and the gene be called bgaC.