Effects of metals on elastase from Pseudomonas aeruginosa SES-938-1

Among the numerous virulance factors produced by Pseudomonas aeruginosa, elastase is the one most often associated with pathogenesis. In this study, effects of various metal ions on elastase from a new isolate of P. aeruginosa (Strain SES-938-1) was investigated. Crude elastase was prepared from culture supernatant via salting out by ammonium sulfate, and then desalting and concentrating the sample using a centricon microconcentrator. Activities were measured at 450 nm using N-succinyl-L-(ala)3-p-nitroanilide as the substrate. The metal chelating agents EDTA and EGTA inhibited the Pseudomonas elastase, which shows that the enzyme is a typical metalloproteinase. At a 10-mM concentration, Mn2+, Ni2+, and Zn2+ strongly inhibited the elastase, whereas Mg2+ effect was negligable. There was a gradual decrease in the enzyme activity in accordance with an increase in the concentration of metal ions.