The extracellular production of a thermolysin inhibitor by 534 wild-type strains isolated from marine sediments and related-type strains was examined. The inhibition of thermolysin activity by strain T-177 was observed on a casein agar medium. According to our detailed taxonomic study, strain T-177 is related to Brevibacillus laterosporus . Further screening for a thermolysin inhibitor was performed using strain T-177 and nine other taxonomically related Brevibacillus type strains, and the ability to produce the inhibitor was observed in five strains. Among these strains, B. reuszeri IFO 15719 T exhibited the highest thermolysin inhibitory activity in broth media, and thus was used for the purification and characterization of the inhibitor. Chromatographic analyses suggested that this substance is a monomeric protein with a molecular mass of 60 kDa.KEY WORDS: Brevibacillus laterosporus , Brevibacillus reuszeri , metalloprotease, protease inhibitors, thermolysin.

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