[Mechanism of action of proteinases of Pseudomonas aeruginosa].

Of the two proteases produced by Pseudomonas aeruginosa, one whose optimal pH is neutral, exhibits elastolytic activity. This elastase is produced as a prepropeptide, subsequently modified by proteolysis, and finally secreted as an active enzyme. Both proteases act mainly on hydrophobic aminoacids. The most important site for the elastase seems to be the P'1 site where Phe, Tyr and Leu residues enhance hydrolysis. The alkaline protease is less specific of this site. At least four aminoacids are needed to obtain measurable rates of hydrolysis. A synthetic substrate, Ala-Ala-Phe-Ala, is proposed for conductimetric measurements of Pseudomonas aeruginosa elastase activities in the nanomolar range. A review of recent studies shows that a very wide range of proteins can be hydrolyzed by the two Pseudomonas aeruginosa proteases, a fact which may explain why these enzymes are major determinants of the bacteria's infectivity.