An extracellular serine protease produced by Vibrio vulnificus NCIMB 2137, a metalloprotease-gene negative strain isolated from a diseased eel

Abstract

Vibrio vulnificus is a ubiquitous estuarine microorganism but causes fatal systemic infections in immunocompromised humans, cultured eels or shrimps. An extracellular metalloprotease VVP/VvpE has been reported to be a potential virulence factor of the bacterium; however, a few strains isolated from a diseased eel or shrimp were recently found to produce a serine protease termed VvsA, but not VVP/VvpE. In the present study, we found that these strains had lost the 80 kb genomic region including the gene encoding VVP/VvpE. We also purified VvsA from the culture supernatant through ammonium sulfate fractionation, gel filtration and ion-exchange column chromatography, and the enzyme was demonstrated to be a chymotrypsin-like protease, as well as those from some vibrios. The gene vvsA was shown to constitute an operon with a downstream gene vvsB, and several Vibrio species were found to have orthologues of vvsAB. These findings indicate that the genes vvp/vvpE and vvsAB might be mobile genetic elements.

Regulation systems of protease and hemolysin production in Vibrio vulnificus

“…Recent studies have shown that a few V. vulnificus strains isolated from diseased eels do not produce VVP because they lack the structural gene vvpE . Interestingly, these strains have been shown to produce a serine protease termed VvsA . VvsA is an orthologue of an extracellular protease produced by V. parahaemolyticus , a causative agent of both human wound infection and gastroenteritis .…”

“…The serine protease from V. parahaemolyticus has been reported to possess various toxic activities such as collagenolytic, cytotoxic, hemolytic and edema‐forming activity . Therefore, VvsA may be one of the critical virulence factors during eel vibriosis, which is characterized by external and internal edematous hemorrhages affecting the major organs .…”

A novel extracellular protease of Vibrio mimicus that mediates maturation of an endogenous hemolysin

“…However, database analysis revealed that only one protein (A5A1168 of V. cholerae strain MZO‐2; accession number AAWF01000039) might be an ortholog of VmtA, suggesting that VmtA is part of a minor group of serine proteases in the Vibrio species. Indeed, the extracellular proteases from V. parahaemolyticus and V. vulnificus are similar to chymotrypsin, but not to trypsin. In Vibrio species, it has been documented that the gene encoding a chymotrpsin‐like protease constitutes an operon with a downstream gene encoding a putative chaperon .…”

“…Indeed, the extracellular proteases from V. parahaemolyticus and V. vulnificus are similar to chymotrypsin, but not to trypsin. In Vibrio species, it has been documented that the gene encoding a chymotrpsin‐like protease constitutes an operon with a downstream gene encoding a putative chaperon . However, we found the vmtA gene was a distinct transcriptional unit, indicating a different maturation mechanism for VmtA.…”

“…In the present study, we purified the novel extracellular protease, termed VmtA, and demonstrated that this protease is a trypsin‐like enzyme. Several Vibrio species, including human pathogens, are known to produce serine proteases . However, database analysis revealed that only one protein (A5A1168 of V. cholerae strain MZO‐2; accession number AAWF01000039) might be an ortholog of VmtA, suggesting that VmtA is part of a minor group of serine proteases in the Vibrio species.…”