Comparative electrophoretic and serological analyses of Vibrio comma and Aeromonas liquefaciens proteinases

Biochemical characterization of extracellular proteases from Vibrio cholerae

Isoelectric focusing of culture supernatants from Vibrio cholerae El Tor 1621 and high protease-producing mutant strain 1621 hip revealed the presence of three different types of extracellular protease. Type I protease was the major activity in the wild-type strain and was inhibited by phenylmethylsulfonyl fluoride and by the lima bean trypsin inhibitor. Type II protease was present in the wild type and was the major activity in the high protease-producing mutant. It was resistant to inhibitors of metalloproteases and serine proteases. Two peaks of type II protease differed by 1.2 pI units in isoelectric point and by 1,500 in molecular weight. Type II protease had broad specificity, acted as a mucinase, and caused degradation of some other V. cholerae extracellular proteins, including DNase and cholera toxin. Type III protease was EDTA inhibitable and was detected only in the high protease producer. Possible roles of extracellular proteases as virulence factors in cholera pathogenesis are discussed.

Characterization of Vibrio cholerae protease activities with peptide digest analysis

A simple method for the analysis of microbial proteases is described that was used to characterize the proteolytic activities of various Vibrio cholerae isolates. This method utilized the unique peptides generated from the degradation of a standard protein by proteases of various specificities. These peptides were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The unique patterns of peptides seen in gels can be used to type proteases according to their relative specificities. Culture supernatants of V. cholerae isolates from a variety of environmental and human sources were analyzed for the presence of a protease previously isolated and characterized in this laboratory from V. cholerae strain CA401. Supernatants from most isolates showing dimethyl casein proteolytic activity exhibited the presence of enzymes similar to the CA401 protease in their peptide digest patterns against bovine serum albumin and in their immunological reactivities. The probable widespread presence of this virulence-associated protease in V. cholerae isolates is discussed.