Proteases secreted by strains of Aeromonas salmonicida

Abstract. The proteases secreted by four strains (MT004, 1102, 480 and 480P^-) of Aeromonas salmonicida grown in liquid culture have been studied. Strains MT004, 1102 and 480 all show a similar pattern with two types of proteases produced; one of molecular weight 70 000 which is active against casein and gelatin and one (or more) of lower molecular weight (about 20 000) which is (are) active against gelatin but not casein. Strain 480P^- produces only the latter type of protease(s). The protease of molecular weight 70 000 is classified as a serine-type protease, but further characterization of the features of its active site has not yet proved possible. The results are discussed in terms of the previously published but often contradictory data on the proteases of A. salmonicida.