PROTEASE PRODUCTION PROFILES OF THE FISH PATHOGEN LISTONELLA-ANGUILLARA BASED ON SUBSTRATE SPECIFICITIES

To determine how many kinds of proteolytic enzymes (proteases) are produced by Listonella anguillora, production profiles were surveyed using synthetic substrates, peptidyl-4-methylcoumaryl-7-amides (MCA substrates). In the qualitative assay, 19 strains of L. anguillara produced protease(s) on 0.5% skim milk agar plate. Ten strains out of 19 were selected to test for the substrate specificites among 13 kinds of MCA substrates. The strains were divided into 3 groups based on their substrate choice as follows: the first group showed high leucine aminopeptidase activity, the second showed high arginine aminopeptidase activity and the third high trypsin like-protease activity hydrolyzing t-butyloxycalbonyl-Leu-Ser-Thr-Arg-MCA (Boc-L-S-T-R-MCA). This indicates that L. anguillara produces several types of proteases. In addition, the growth and protease production of the organisms with time were examined. It was found that leucine aminopeptidase is a post-growth phase enzyme in all the 3 strains tested, whereas the secretion kinetics of arginine aminopeptidase and trypsin like-protease were different in different strains.