Structural and Functional Analysis of the Serine Protease from Aeromonas sobria

Aeromonas species are Gram-negative facultative anaerobic bacteria found ubiquitously in a variety of aquatic environments and most commonly implicated as causative agents of gastroenteritis. Sepsis is a fatal complication of Aeromonas infectious diseases, particularly in immune-compromised patients. Two species, Aeromonas hydrophila and Aeromonas sobria, are associated with human disease. Feasible virulence factors of Aeromonas include fimbrial and afimbrial adhesion molecules, hemolysins, enterotoxins, lipases and proteases. Recently, we purified a 65-kDa A. sobria serine protease (ASP) from the culture supernatant of A. sobria and found that the enzyme induces vascular leakage and reduces blood pressure through activation of the kallikrein/kinin system. This ASP activity potentially contributes to the onset of septic shock, suggesting ASP as an important virulence factor. In this review, I describe both the substrate specificity and the structural property of ASP. Furthermore, I also discuss the maturation mechanism of ASP. Further studies will facilitate development of novel drugs for bacterial infection that have inhibitory effects on various serine proteases.