Immunochemical investigation of four Saprolegnia species with parasitic activity in fish: Serological and kinetic characterization of a chymotrypsin-like activity.

The antigenic structure of four aquatic Phycomycetes of the genusSaprolegnia with parasitic activity in fish was analyzed with immunoelectrophoresis and double diffusion techniques. It is shown that these serological tests might represent a valuable criterion for the identification of the fourSaprolegnia species:S. parasitica, S. ferax, S. delica, andS. diclina. A specific chromogenic reaction revealed the presence of a protease with chymotrypsin-like activity among the precipitation arcs obtained after immunoelectrophoresis. Analysis of this proteolytic activity by kinetic assay methods confirmed the results of the serological tests. Moreover estimates of the quantity of enzyme present in the cellular extract and in the culture medium were obtained. A possible relationship between the proteolytic activity and the host-parasite interaction was discussed.