Isolation and characterization of a protease from Bacteroides gingivalis

A protease was purified from Bacteroides gingivalis ATCC 33277 culture fluid by sequential procedures including ammonium sulfate precipitation, ion-exchange chromatography, and isoelectric focusing. The enzyme was active against benzoyl-L-arginine-p-nitroanilide, carbobenzoxy-L-phenylalanyl-L-valyl-L-arginine-p-nitroanilide azoalbumin, azocasein, azocoll, and p-tosyl-L-arginine methyl ester. The molecular weight of the enzyme was about 300,000 as determined by gel filtration. Its isoelectric point was 5.0. The maximum activity was found at pH 7.5, and the optimum temperature for activity was between 40 and 45 degrees C. The apparent Km value for benzoyl-L-arginine-p-nitroanilide was 2 mM. The enzyme was inhibited by sulfhydryl group-blocking reagents, tosyl-L-lysine chloromethyl ketone, and EDTA. Soybean trypsin inhibitor and diisopropylfluorophosphate were not inhibitory.