Pathogenesis of serratial infection: activation of the Hageman factor-prekallikrein cascade by serratial protease.

A serratial protease with an apparent molecular weight of 56,000 (56K protease), which had been purified from the culture supernatant of a strain of Serratia marcescens isolated from a corneal lesion of a human eye [Matsumoto, K. et al. (1984) J. Bacteriol. 157, 225-232], greatly enhanced vascular permeability when injected into guinea pig skin. The 56K protease, which requires zinc ion for activity, was found to possess plasma kallikrein-like properties in vitro as judged by (i) preferential amidolysis of carbobenzoxy-Phe-Arg-4-methylcoumaryl-7-amide and Pro-Phe-Arg-4-methylcoumaryl-7-amide, which are known substrates for plasma kallikrein; (ii) release of kinin from high-molecular-weight kininogen; and (iii) prompt activation of Hageman factor followed by generation of kallikrein from plasma prekallikrein. These results suggest that the 56K protease enhances vascular permeability through activation of a Hageman factor-kallikrein-kinin pathway in vivo, and this molecular process appears to be a rational mechanism of enhancement of permeability and serratial pathogenesis.