Aim and Background . Metalloproteases have numerous industrial applications such as peptide and aspartame synthesis. However, their application is limited by instability as a result of autolysis. . In the present study, following purification, biochemical properties of a metalloprotease (elastase) from Pseudomonas aeruginosa have been investigated.

Materials and Methods. Recombinant protein has been purified from E. coli by affinity chromatography. Temperature dependence of enzyme activity and optimum temperature has been measured using a plot of enzyme activity versus different temperatures. Optimum temperature of enzyme activity has been determined within a mix buffer solvent by activity measurements at different pHs, and the inactivation rate, t_1/2 and thermodynamic parameters of inactivation have been determined using irreversible thermoinactivation.

Results. Optimum temperature was 60°C in the presence of 0, 5 and 10 mM CaCl₂, and optimum pH was 8.5. Inactivation rate was increased with elevation of temperature from 55 to 80°C. Half-life of thermoinactivation ( t_1/2 ) was 150, 112, 47, 32, 18, 8 and 4 min at 55, 60, 65, 70, 75 and 80°C, respectively. E_a, D H ^# , D S ^# and D G ^# was 37.70, 37.02, 23.61 kcal/mol, respectively, and k_inactivation was 4.49 ´ 10³ s^-1.

Conclusion . Pseudomonas aeruginosa elastase can be considered between thermophilic and mesophilic enzymes. Optimum temperature did not alter in different calcium concentrations which imply that elastase stability is Ca-independent.