Genes for an alkaline D-stereospecific endopeptidase and its homolog are located in tandem on Bacillus cereus genome

Alkaline D-peptidase (Adp) from Bacillus cereus DF4-B is a D-stereospecific endopeptidase acting on oligopeptides composed of D-phenylalanine and the primary structure deduced from its gene, adp, shows a similarity with D- stereo specific hydrolases from Ochrobactrum anthropi strains. We have isolated DNA fragments covering the flanking region of adp from DF4-B genome and found an additional gene, adp2, located upstream of adp. The deduced amino acid sequence of Adp2 showed 96% and 85%, identity with those of Adp from B. cereus strains AH559 and DF4-B, respectively. The recombinant Adp2 expressed in Escherichia coli was purified to homogeneity and characterized. It had hydrolyzing activity toward (D-Phe)(3), (D-Phe)(4), and (D-Phe)(6) but did not act on (L-Phe)(4), D-Phe-NH2, and L-Phe-NH2, some characteristics that are closely related to those of Adp from strain DF4-B. These results indicate that highly homologous genes encoding D-stereospecific endopeptidases are arranged in a tandem manner on the genomic DNA of B. cereus DF4-B. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.