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.

Aim and Background:Proteases have multiple applications within organic media, and then their organic solvent stability is critically important. Pseudomonas aeruginosa elastase is an organic solvent stable enzyme. In the present work, following protein purification, its organic solvent activity and stability have been investigated. 

Materials and Methods:Protein purification was carried out by affinity chromatography. Enzyme activity within organic solvent media has been measured by activity measurements in the 0-70% (V/V) of organic solvents including ethanol, methanol, isopropanol, dimethyl formamide (DMF), glycerol and ethylene glycol.

Results: In the presence of all concentrations of organic solvents investigated in the present study, except ethanol, activity of elastase was very high and even higher than that of control, i.e. in the absence of organic solvents. For instance, in the presence of 70% (V/V) of methanol, DMF and glycerol enzymatic activity was 3.5, 1.4 and 1.2 times higher than that of 0% of organic solvents. 

 Conclusion: On the contrary to most enzymes whose activity diminishes in organic solvents, the present study clearly indicated that elastase activity increases even in the presence of organic solvents. This finding means that Pseudomonas aeruginosa elastase is not only an organic solvent enzyme, but more ideal catalyst within aqueous-organic than absolutely aqueous medium.