Different enzymatic oscillations in vivo caused by the stereoisomers of an aminopeptidase inhibitor, bestatin.

The present study was undertaken to compare the enzymatic oscillations induced in three major organs, spleen, kidney, and liver, of mice by the active and inactive forms of an aminopeptidase inhibitor, bestatin. Although bestatin caused sine curve-type oscillations of enzymatic activities in spleen and kidney, its isomer, possessing no enzyme-inhibiting actions and no biological actions, did not show any typical enzymatic changes. Such typical oscillations were not elicited by either one of those two agents in liver, in spite of the apparent difference in the type of oscillations induced by them in this organ. These observations were taken to indicate that the enzymatic oscillations in vivo caused by bestatin are closely related to its aminopeptidase-inhibiting actions seen in vitro and that the immunomodifying actions of this agent are based on its effects on enzymes sensitive to it, possibly involving immunoresponsive cells.