Purification and characterization of an extracellular protease from the fish pathogen Yersinia ruckeri and effect of culture conditions on production

• Published in: Applied and Environmental Microbiology Vol. 65; no. 9; pp. 3969 - 3975
• Main Authors: Secades, P, Guijarro, J.A
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01-09-1999
• Subjects: Animals; Bacteriology; Biological and medical sciences; Caseins - metabolism; Culture Media; Endopeptidases - isolation & purification; Endopeptidases - metabolism; enzyme activity; Enzymes; Enzymology and Protein Engineering; Fish; Fish Diseases - microbiology; Fishes; Fundamental and applied biological sciences. Psychology; Immunoblotting; Microbiology; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Protease Inhibitors - pharmacology; proteinases; proteolysis; Temperature; Yersinia - enzymology; Yersinia - growth & development; Yersinia Infections - microbiology; Yersinia Infections - veterinary; Yersinia ruckeri; Purification; Enzyme; Virulence; Peptidases; Vertebrata; Yersinia ruckeri; Pathogenic; Pisces; Bacteria; Hydrolases; Mutation; Kinetic parameter; Physicochemical properties; Enterobacteriaceae
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/aem.65.9.3969-3975.1999

A novel protease, hydrolyzing azocasein, was identified, purified, and characterized from the culture supernatant of the fish pathogen Yersinia ruckeri. Exoprotease production was detected at the end of the exponential growth phase and was temperature dependent. Activity was detected in peptone but not in Casamino Acid medium. Its synthesis appeared to be under catabolite repression and ammonium control. The protease was purified in a simple two-step procedure involving ammonium sulfate precipitation and ion-exchange chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the purified protein indicated an estimated molecular mass of 47 kDa. The protease had characteristics of a cold-adapted protein, i.e., it was more active in the range of 25 to 42 degrees C and had an optimum activity at 37 degrees C. The activation energy for the hydrolysis of azocasein was determined to be 15.53 kcal/mol, and the enzyme showed a rapid decrease in activity at 42 degrees C. The enzyme had an optimum pH of around 8. Characterization of the protease showed that it required certain cations such as Mg(2+) or Ca(2+) for maximal activity and was inhibited by EDTA, 1,10-phenanthroline, and EGTA but not by phenylmethylsulfonyl fluoride. Two N-methyl-N-nitro-N-nitrosoguanidine mutants were isolated and analyzed; one did not show caseinolytic activity and lacked the 47-kDa protein, while the other was hyperproteolytic and produced increased amounts of the 47-kDa protein. Azocasein activity, SDS-PAGE, immunoblotting by using polyclonal anti-47-kDa-protease serum, and zymogram analyses showed that protease activity was present in 8 of 14 strains tested and that two Y. ruckeri groups could be established based on the presence or absence of the 47-kDa protease.