Abstract

An extracellular protease of Salmonella schottmulleri was purified from culture filtrate by using 0-75% ammonium sulfate precipitation, DEAE Sepharose Fast Flow ion exchange chromatography, Ultrogel HA chromatography and Sephacryl S-200 HR molecular sieve chromatography. To measure enzyme activity, synthetic dipeptide substrate (CBZ-arg-arg-AFC) with low molecular weight was employed as substrate. The molecular weight of the purified enzyme was approximately 80 kDa when determined by gel filtration on Sephacryl S-200 HR and 73 kDa when estimated by SDS-PAGE. The isoelectric point was 5.45. The activity of the purified enzyme was inhibited by metal chelating agesnts such as EDTA and 1.10-phenanthroline. The divalent cations, such as Ca^2+, Zn^2+, Fe^2+, Mg^2+ enhanced its activity. These results suggested that it was a metalloprotease. It had a narrow pH optimum of 6.5-7.5 with a maximum at pH 7.0 and a temperature optimum of 40℃. It was stable at least for 1 week at 40℃ and maintained its activity for 24 hours at 50℃, but it was rapidly inactivated at 65℃. This protease was shown to be sensitive to sodium 50℃, but it was rapidly inactivated at 65℃. This protease was shown to be sensitive to sodium 50℃, but it was rapidly inactivated at 65℃. This protease was shown to be sensitive to sodium 50℃, but it was rapidly inactivated at 65℃. This protease was shown to be sensitive to sodium dodecyl sulfate (SDS) and was inactivated in a dose-dependent manner. However, it was resistant to Triton X-100 and the activity was enhanced to 32.3% with treatment of 0.025% Triton X-100.

• Keywords: purification; characterization; extracellular protease; S. schottmulleri