The present invention is directed to an .alpha. thio-containing compound that is capable of inhibiting the enzyme, membrane aminopeptidase P (mAPP or APP), whose natural substrate is bradykinin. The compound is useful as a pharmaceutical agent because by inhibiting bradykinin degradation, the compound allows bradykinin to exert its beneficial effects on the cardiovascular system, to improve renal function, and to improve glucose tolerance and insulin-sensitivity. The present invention is also directed to a pharmaceutical composition comprising the mAPP inhibitor of the present invention and a pharmaceutically acceptable carrier. In another aspect, the present invention is directed to a method of inhibiting bradykinin degradation in a mammalian patient, preferably human, in need of treatment comprising administering to the patient a therapeutically effective amount of an .alpha. thio-containing compound of the present invention. The method of the present invention also contemplates the further step of administering to the mammalian patient in need of treatment a therapeutically effective amount of an inhibitor of angiotensin converting enzyme (ACE).