Metalloproteases of Serratia liquefaciens: degradation of purified human serum proteins.

Two representative strains of Serratia liquefaciens, SL 5 (serotype O5:H1) and SL 11 (serotype O1:H1), produced proteases characterized by molecular weights of 52.5 kilodaltons and isoelectric points of 6.2; both enzymes were inhibited by 50 mM EDTA. As demonstrated with SDS-PAGE electrophoresis, the two metalloproteases attacked the following purified human serum proteins: complement components C3, C4, C5, C6, C7, C8, and C9, transferrin, alpha 1-antitrypsin, alpha 2-macroglobulin, fibronectin, type III fibrinogen, immunoglobulin G (heavy chains), and IgM (heavy chains). However, C1q, IgA, haptoglobin, and C-reactive protein were refractory.