Proteolytic activity which is inhibited in the presence of o-phenanthroline was found in M. morganii ZM. Intracellular proteases of M. morganii ZM unlimited split musculoskeletal actin in contrast to grimelysin. Several proteolitic proteins of M. morganii ZM cells were identified by zymography with gelatin. Metalloproteinase of M. morganii ZM cell lysate was purified by hydrophobic chromatography fractionation. The molecular weight of the protein was 35 kDa.