Short peptides based on the tripeptides,Leu-Arg-Pro and Leu-Lys-Pro,were synthesized by microwaveassisted solid-phase synthesis method,in order to make a search for potential inhibitors for angiotensin (I)-converting enzyme(ACE) with minimum side effects in the treatment of hypertension.One peptide with the sequence Leu-Arg-Pro-Phe-Phe shows the strongest inhibition towards ACE with an IC50 value of 0.26 μmol/L in vitro.The study of structure-activity relationship shows that the introduction of a bulky group into the N-terminal of this series of inhibitors may enlarge steric hindrance,resulting in the poor inhibitory activity towards ACE.The inhibitory activity decreased in turn when L-Pro,D-Pro or Ac6c was at the C-terminal respectively.The binding interaction between each of these inhibitors and testicular ACE(tACE) was performed by molecular docking.The results suggest that Leu-Arg-Pro-Phe-Phe mainly occupied the St subsite of tACE,and made contact with tACE via seven H-bonds.It appeared that the site on the peptide that bound with tACE was influenced by the configuration of the amino acid,L- or D-form,at the C-terminal of the peptide.