NEW THIOL INHIBITORS OF NEUTRAL ENDOPEPTIDASE EC-3.4.24.11 - SYNTHESIS AND ENZYME ACTIVE-SITE RECOGNITION

Selective, as well as mixed, inhibitors of the two zinc metallopeptida ses, neutral endopeptidase (NEP) and angiotensin converting enzyme (AC E), are of major clinical interest in the treatment of hypertension an d cardiac failure. New thiol inhibitors, corresponding to the general formula HS-CH(R(1))-CH2-CH(R(2))-CONH-CH(R(3))-COOH, were designed in order to explore the putative S-1 subsite of the active site of NEP. T he inhibitors were also tested on ACE and the most representative on t hermolysin (TLN) for comparison. The relatively low inhibitory potenci es exhibited by these compounds (IC(50)s in the 10(-7) M range for NEP and in the 10(-6) M range for ACE) as compared to that of thiorphan ( IC(50)s 2 10 X 10(-9) M on NEP and 1.40 x 10(-7) M on ACE) clearly ind icate the absence of the expected energetically favorable interactions with the active site of both peptidases. A 100-fold loss of potency f or these inhibitors was also observed for thermolysin as compared to t hiorphan. Using the mutated Glu(102)-NEP, it was possible to demonstra te that the inhibitors do not fit the S-1 subsite of NEP but interact with the S-1' and S-2' subsites through binding of their R(1) and R(2) residues and that the C-terminal amino acid is located outside the ac tive site. These results seem to indicate that these thiol inhibitors are not well. adapted for optimal recognition of the S-1 subsite of NE P, and probably ACE, and that other zinc-chelating moieties such as ca rboxylate or phosphonate groups may be preferred for this purpose.