Histochemistry of exopeptidase activity in the brain using a natural substrate method

: The location and properties of brain exopeptidase activities are determined with the method of so-called natural substrates. The activities of enzymes cleaving dipeptides (leu-leu, tyr-tyr, tyr-phe, met-ala, met-arg and gly-pro) are compared with both the activities and character of enzymes cleaving chromogenic leu-4M2NA substrate. The present work demonstrates a broad spectrum of exopeptidase activities localized in glia, neurons, neuropile and cerebral vessels. The cleavage of tyr-tyr and tyr-phe substrates is preferred with exopeptidases localized in neurons and their fibrillar protrusions. The leu-leu and leu-4M2NA substrates are cleaved in some definite portions of capillaries and thicker vessels. In the present work the question is discussed of substrate specificities of determined enzymatic activities in relation with detection specificity of M aminopeptidase.