Isolation of a new toxic protease from a strain of Aeromonas salmonicida subspecies achromogenes

Abstract

A new toxic protease was isolated from Aeromonas salmonicida subspecies achromogenes extracellular products (ECP). It was detected in 5 of 9 strains of the organism tested. The protease was purified by anion-exchange fast protein liquid chromatography (FPLC) on Mono Q HR 5/5, and FPLC gel filtration on Superose 12 HR 10/30. The LD/50 of the purified protease for juvenile Atlantic salmon Salmo salar was 0.03 µg protein g-1 fish. The molecular weight of the protease was estimated to be 20 kD by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and it possessed 2 isoelectric points (pls) of 6.2 and 6.4. The protease was completely inhibited by EDTA indicating it to be a metallo-protease.