The effect of NaCl concentration (0--0.15 mol L-1) and gamma-irradiation dose on the catalytic activity of the angiotensin-converting enzyme is considered. Special regions in which a particular mechanism of dose response predominates are identified. In acid and alkaline media, there are regions of substantial enzymic activation; in addition, damped oscillations of the enzymic activity are observed. At pH 7.5, when the enzyme adopts;I more "unfolded" conformation, the clearly defined activation peaks on the surface relief are smoothed over, indicating a decrease in the effect of the salt concentration.