Studies on Protease Activities of the Nemertean Procephalothrix simulus

The effects of temperature,pH and feeding on the protease activity of Procephalothrix simulus were studied.The results showed that the peaks of protease activities appeared at pH values of 3 and 10,and the activity of acid protease was higher than that of alkaline protease.The effect of temperature(20～80 ℃) on acid protease activity was different from that on alkaline protease.Acid protease activity reached the peak value at 50 ℃;while for the alkaline protease,the optimal temperature was 40 ℃,and the activity decreased rapidly when the temperature was elevated to 50 ℃,which indicated that the alkaline protease was sensitive to high temperature.The results also showed that the protease activity of P.simulus varied significantly after feeding.After being elevated to its maximum value 2 h after feeding,the activity of acid protease declined and reached the lowest value at 8 h,then the activity increased again and became stabilized 24 h after feeding.Alkaline protease,however,increased to the peak value at 8 h,and remained at low levels 16 h after feeding.