Variations in rat dipeptidase activity following parenteral administration of activator and inhibitor.

One of the more prominent characteristics of intracellular peptidases is their remarkable susceptibility to the presence in the hydrolysis mixture of specific activators and inhibitors. The present investigation was undertaken to determine whether these relationships would remain unchanged if the activator or inhibitor were injected into the intact animal prior to the removal of the tissue to be examined. The enzymic hydrolysis of glycylglycinel (GG) by rat plasma and muscle was selected for study since this dipeptidase (GGase) activity is strongly activated by cobalt and inhibited by cysteine (1). In addition, there is available a technique (2) which provides a measurement of GGase activity in surviving rat diaphragm; thus conditions which presumably simulate more closely those in the intact animal may be obtained.