Purification, bacteriolytic activity, and specificity of β-lytic protease from Lysobacter sp IB-9374

Lysobacter sp. IB-9374, which was isolated from soil as a high lysyl endopeptidase-producing strain (Chohnan et al., FEMS Microbiol. Lett., 213, 13-20, 2002), was found to produce a beta-lytic protease capable of lysing gram-positive bacteria such as Staphylococcus aureus, Microccocus luteus, and Bacillus subtilis. The Lysobacter strain secreted the beta-lytic protease into the culture medium at a 2.4-fold higher level than Achromobacter lyticus. The enzyme was highly purified through a series of six steps with a high yield. The enzyme was strongly inhibited by tetraethylenepentamine and 1,10-phenanthroline. The purified enzyme lysed more efficiently almost all the grain-positive bacteria tested than lysozyme, lysostaphin, and mutanolysin. The enzyme was very similar to Achromobacter beta-lytic protease containing one zinc atom in terms of amino acid composition and N-terminal sequence. The nucleotide sequence revealed that the mature enzyme was composed of 179 amino acid residues with additional 198 amino acids at the amino-terminal end of the enzyme. The deduced amino acid sequence of the mature enzyme coincided with that of the Achromobacter enzyme, although the prepro-region showed a 41% sequence identity with the counterpart. These results indicate that Lysobacter sp. is a useful strain for an efficient large-scale preparation of beta-lytic protease capable of lysing bacteria.