Identification of an elastolytic protease in stationary phase culture filtrates of M. tuberculosis.

Culture filtrate from M. tuberculosis grown in Sauton broth was screened at weekly intervals for elastase and caseinase activity. Both activities were detected concomitantly at 4 weeks and had similar inhibitor and pH profiles. Highest activity occurred between pH 6.5 and pH 7.5. Azocaseinase activity was linear with time between 12 and 28 h at 37 degrees C. Enzymatic activity was inhibited by EDTA, EGTA, dithiothreitol, ethylmaleimide, 1,10-phenanthroline, Zincov, N-tosyl-L-phenylalanine chloromethyl ketone, and N-methoxysuccinyl-Ala-Ala-Pro-Val chloromethyl ketone. SDS-PAGE analysis revealed breakdown of casein after incubation with culture filtrate. These results indicate the presence of a calcium-dependent, elastolytic metalloprotease in stationary phase cultures of M. tuberculosis.