PURIFICATION AND PARTIAL CHARACTERIZATION OF 2 EXTRACELLULAR ALKALINEPROTEASES FROM STREPTOMYCES-CORCHORUSII ST36

Two distinct alkaline proteases were detected in the culture medium of Streptomyces corchorusii ST36 isolated from an Egyptian soil sample. These enzymes were purified by precipitation with chilled ethanol and gel filtration on carboxymethyl Sepharose and on Sephadex G-120. The e nzymes were purified 6 and 6.5 fold to homogeneity. The purified enzym es had final specific activities on substrate of 3.6 and 3.9 U/mg. Pro tease 1 had a molecular mass of 31 kDa and protease 2 was composed of two subunits, of molecular masses 18.6 and 17.4 kDa. The optimal pH an d temperature for catalytic activity of protease 1 were pH 11 and 70 d egrees C, respectively, and for protease 2 they were pH 10 and 70 degr ees C, respectively. Protease 1 was more thermostable than protease 2. Both enzymes showed substrate specificity to casein, serum albumin, a nd ovalbumin. Calcium, copper, and cobalt stimulated protease 2 but di d not significantly affect protease 1. Mercury was the strongest inhib itor for protease 2. The proteolytic activities of both proteases were inhibited by 10 mM phenanthroline and 50 mM ethylenediaminetetraaceti c acid (EDTA). The inhibitory effect of EDTA on both enzymes was rever sed by the addition of 50 mM of copper, calcium, or cobalt. Both enzym es were more stable at - 20 degrees C under alkaline conditions than u nder neutral or acidic conditions.