SECRETED PROTEASES FROM ACTINOBACILLUS-PLEUROPNEUMONIAE SEROTYPE-1 DEGRADE PORCINE GELATIN, HEMOGLOBIN AND IMMUNOGLOBULIN-A

It was found that 48 hour cultures of Actinobacillus pleuropneumoniae secreted proteases into the medium. Electrophoresis in polyacrylamide gels (10%) copolymerized with porcine gelatin (0.1%), of the 70% (NH4) (2)SO4 precipitate from the culture supernatants, displayed protease a ctivities of different molecular weights: >200, 200, 90, 80, 70 and 50 kDa. They had activity over a broad range of pHs (4-8), with an optim al pH of 6-7. All were inhibited by 10 mM EDTA, and reactived by 10 mM calcium. They were stable at -20 degrees C for more than a month. The proteases also degraded porcine IgA and porcine, human, and bovine he moglobin, although they appeared to be less active against the hemoglo bins. The IgA was totally cleaved in 48 h, using supernatants concentr ated with polyvinyl pyrrolidone or the 70% (NH4)(2)SO4. Extracellular proteases could play a role in virulence.