[en] Purified elastase was obtained from clinical Pseudomonas Aeruginosa (P.A.-283). The enzyme showed not only elasto lytic activity, but also a broad proteolytic activity against various proteins. The activity of the enzyme on collagen and gelatin was also observed. The optimum pH for elastase was 7.8 to 8.0 for both the proteolytic and elasto lytic activities. The elastase was stable in a pH range from 6.6 to 9.0. Optimum temperature for proteolytic and elasto lytic activities was 40 and inhibition of elastase occurs at 80 . The D₁0 value of the P.A-283 was found to be 0.11 kGy. Increasing the dose level value of gamma-irradiation decrease the proteolytic activity in the culture filtrate reaching only 16% at the dose level 0.5 kGy. Chelating agents and some metal ions inhibited both proteolytic and elasto lytic activities. Selective inhibition of elasto lytic activity was observed in high concentrations of sodium and ammonium salts without concurrent decrease in the proteolytic activity of the enzyme.4 fig., 3 tab