PURPOSE: To prepare a carcinostatic enzyme, by treating a proteinase produced in the emergence of silkworm moth with a slightly acidic organic acid, thereby purifying the enzyme to a cathepsin-type oxidase.

CONSTITUTION: The chrysalis in the cocoon 1 emerges 4 by dissolving the sericin and fibroin constituting the cocoon layer by the enzyme excreted from the chrysalis. After emergence, the part 3 of the cocoon 1 contacting with the emergency enzyme is cut off at the line 2 to obtain a piece of cocoon 6 containing the emergency enzyme. The cocoon 6 is put into the extraction vessel 5 and immersed in tepid water at 30W35°C to extract the emergency enzyme which is a proteinase. The extracted liquid is transferred to the stirring tank 7 and chemically treated with a slightly acidic organic acid 10 in a manner to prevent the enzyme from inactivation. The treated enzyme is purified in the purifying tank 8 and activated as a cathepsin-type oxidase 9 to obtain the objective carcinostatic enzyme solution.