Novel mechanism of inhibition of human angiotensin-I-converting enzyme (ACE) by a highly specific phosphinic tripeptide

Abstract

Human ACE (angiotensin-I-converting enzyme) has long been regarded as an excellent target for the treatment of hypertension and related cardiovascular diseases. Highly potent inhibitors have been developed and are extensively used in the clinic. To develop inhibitors with higher therapeutic efficacy and reduced side effects, recent efforts have been directed towards the discovery of compounds able to simultaneously block more than one zinc metallopeptidase (apart from ACE) involved in blood pressure regulation in humans, such as neprilysin and ECE-1 (endothelin-converting enzyme-1). In the present paper, we show the first structures of testis ACE [C-ACE, which is identical with the C-domain of somatic ACE and the dominant domain responsible for blood pressure regulation, at 1.97Å (1 Å=0.1 nm)] and the N-domain of somatic ACE (N-ACE, at 2.15Å) in complex with a highly potent and selective dual ACE/ECE-1 inhibitor. The structural determinants revealed unique features of the binding of two molecules of the dual inhibitor in the active site of C-ACE. In both structures, the first molecule is positioned in the obligatory binding site and has a bulky bicyclic P1′ residue with the unusual R configuration which, surprisingly, is accommodated by the large S2′ pocket. In the C-ACE complex, the isoxazole phenyl group of the second molecule makes strong pi–pi stacking interactions with the amino benzoyl group of the first molecule locking them in a ‘hand-shake’ conformation. These features, for the first time, highlight the unusual architecture and flexibility of the active site of C-ACE, which could be further utilized for structure-based design of new C-ACE or vasopeptidase inhibitors.

The toxicity of angiotensin converting enzyme inhibitors to larvae of the disease vectors Aedes aegypti and Anopheles gambiae

“…Our extensive knowledge from high resolution structural studies on how inhibitors interact with both the N- and C-domains of human ACE and insect ACE2549505152535455565758 has revealed the molecular basis of binding features of the inhibitors and highlights differences in the inhibitor-enzyme interaction of insect ACE compared with the active sites of the human enzyme. Using the AnoACE homology models and amino acid sequence alignment, it is possible to compare different ACE proteins to look for residue and environment differences in both AnoACE2 and AnoACE3, which could be targeted to create specific inhibitors against these enzymes.…”

Crystal structures of highly specific phosphinic tripeptide enantiomers in complex with the angiotensin‐I converting enzyme

“…Overall, FI and FII are both strong inhibitors of C‐ACE with similar potency ( K i = 0.41 ± 0.03 and 0.61 ± 0.03 n m , respectively ). The overall binding mechanism has some common features with other phosphinic inhibitors but shows key differences at the P 1 ' site, with C‐ACE accommodating the S configuration of FI through hydrophobic interactions with the S 1 ' cavity.…”

“…The ACE/ECE‐1 FI dual inhibitor is a competitive inhibitor of both N‐ACE and C‐ACE. However, it is ~ 440‐fold more selective for C‐ACE (apparent K i = 0.41 ± 0.03 n m ). One bound inhibitor molecule was modelled in the catalytic site of C‐ACE (Fig.…”

“…As in the C‐ACE with FII structure , FI occupies all four substrate binding subsites (S 2 , S 1 , S 1 ′ and S 2 ′) and two phosphinic oxygen atoms (OAG and OAD) of the inhibitor make direct coordination with the catalytic zinc ion (distance 2.2 and 2.4 Å respectively) at the active site. In addition, it is held by 12 hydrogen bonds including four hydrogen bonds mediated through water molecules, as calculated by hbplus (Table ).…”

“…Comparison between the stereoisomers FI and FII binding to angiotensin‐I converting enzymes: (A) FI (purple) and FII (pink, PDB 2XY9 ) bound to C ‐ ACE (cyan); (B) FI and FII ( PDB 2XYD ) bound to N ‐ ACE (teal); (C) FI and FII bound to A n CE (green). Stereo representations of the structures in complex with FI and FII for each protein (aligned in pymol , all atoms superposition) and residues shown are from the enzymes in their respective complexes with FI only.…”