The enzymatic activity of proteinase which was isolated from a shell fish, Veneridae Soxidomus purpuratus Sowerby(Korean name "Gai-jo-gai") was studied, and the obtained results were as follows; (1) The optimum pH of the enzyme was around 7.5 (2) The prohibiting activity of metalic ions for the enzymatic activity was the order of 1/1000M-$Ag^{+}$>1/1000M-$Zn^{++}$>1/1000M-$Cd^{++}$>1/1000M-$Pb^{++}$. (3) Of 3 specimens of the enzyme from heptapancreas, gastro-intestine and crystalline style the highest activity was shown by one from crystalline style.