Chemical design of antihypertensive agent as a potent inhibitior of angiotensin I-converting enzyme

Abstract

A novel form of antihypertensive agent was developed by a chemical design based on specific inhibitor of Angiotensin I-converting enzyme (peptidyldipeptide hydrolase, EC 3.4.15.1) since this enzyme plays key role in the regulation of blood pressure through the Renin-Angiotensin-Aldosterone system. The activity of partially purified hogplasma enzyme was assayed by using a trichlorotriazine method, a direct spectrophotometric assay based on the specific colorimetric reaction of liberating hippuric acid with 2,4,6-trichloro-s-triazine. The enzyme was found to be inhibited by SH-group containing compounds without structural characteristics. Inhibition study with glycyl dipeptides and alanyl dipeptides revealed that a free COOH-terminal moiety of the peptides was of importance to the overall binding of the peptides to the enzyme active site. Among the test dipeptides, Val-Trp acted as the most potent inhibitor. Based on the structure-activity correlations and oral effectiveness, a compound N-benzyl-L-cysteinyl-L-proline was designed as a potent inhibitor of Angiotensin I-converting enzyme, and its chemical synthesis was accomplished by a conventional peptide synthetic method. From the kinetic study, the synthetic compound, N-bzl-Cys-Pro, was found to be potent competitive inhibitor with Ki value of $2.3\times10^{-6}$M and $ID_{50}$ of $5.7\times10^{-6}$M (kM for HHL was $2.5\times10^{-3}$M)