Halophilic bacterium, producing two extracellular proteases, was isolated from Badab-Sourt, Iran. 16S rDNA analysis shown high similarity with the genera Idiomarina. Maximum secretion of enzymes was observed during the early-stationary phase of bacterial growth. Both extracellular proteases were purified by three purification steps; ammonium sulfate precipitation, Q-Sepharose, and Sephadex G-200 chromatography columns. The molecular weight of purified enzymes was determined by SDS-PAGE gel electrophoresis with approximate masses of 48 and 51 kDa (45.57 and 80.30 U/mg specific activity). Proteases synthesized by strain S-18 were affected by medium compositions. Optimum concentration of substrate, pH, and temperature for both enzymes activity were 0.5% casein, 9.0, and 50 °C. However, purified proteases showed different activity at various salt concentrations, which their maximum activity was determined in the presence of 7.5 and 5% NaCl. The activity of enzymes increased in the presence of metal ions such as Mn2+ and Cu2+ and decreased by the presence of Hg2+ and Fe2+. Both proteases were strongly inhibited by SDS, while DDT, EDTA, and 2-Mercaptoethanol could stimulate their activity. The results of present research might be interesting issue for industrial applications and biotechnological processes.
