Some physico-chemical properties of proteolytic enzyme produced from Streptomyces alboniger Hesseltine were characterized. The optimal pH and temperature of the enzyme; were around pH 9.0 and 40℃, respectively. The enzyme was stable between pH 6.0∼10.8 and the enzyme activity was not inactivated by heat treatment in lower temperature than 40℃. However the enzyme activity decreased by 70% of the initial activity for 10minutes at 70℃. The Km value was 7.1μM with Hammarsten casein and 333.3μM with cytochrom C. The activity of enzyme was inhibited by metal ions in the order of Fe^(+++)$gt;Hg^(++)$gt;Cu^(++$gt;Pb^(++)$gt;Zn^(++), whereas Ca++ increased the enzyme activity. There was no effect of Mg^(++) and Co+t on the enzyme activity. The enzyme was inhibited by EDTA strongly. When Ca^(++) was added to the EDTA-denaturated enzyme, the activity of enzyme was restored.