PURPOSE: The titled inhibitor to inhibit all enzymatic activities of five decomposing enzymes existing in organisms, comprising angiotensin III as an active ingredient.

CONSTITUTION: The titled activator comprising angiotensin III well-known as a substance in organisms, having pressor action and secreting action on aldosterone. The compound inhibits all enzymatic activities of five anzymes of aminopeptidase to scissor Tyl-Gly bond of enkephalin, dipeptidyl aminopeptidase A and B to scissor Gly-Gly, angiotensin converting enzyme to scissor Gly-Phe bond, and enkephalindipeptidyl carboxypeptidase. A pain is alleviated by admininstering the activator to a patient with pain caused by reduction in enkephalin, and excellent analgesic action is developed in a patient with chronic pain with especially low content of enkephalin in the brain.