Design and evaluation of four novel tripeptides as potent angiotensin converting enzyme (ACE) inhibitors with anti-hypertension activity

•In this study, ACE inhibitory activity and mode of four novel tripeptides had been explored.•TTP and gAgAP induced rapid and significant reductions of systolic blood pressure in SHRs.•TTP treatment led to a comparable reduction of agtr1 levels but a significantly lower expression of miR-132/212. The current study investigated the angiotensin-converting enzyme (ACE) inhibitory activity of 4 synthetic tripeptides. All the peptides showed enzyme inhibitory activity, especially two promising ones, TTP (Thea-Thea-Pro) and gAgAP (GABA-GABA-Pro), with IC50 values of 0.92 and 3.4 μmol/L, respectively. Enzyme inhibition kinetics determined by Lineweaver-Burk plots revealed that TTP and gAgAP were competitive inhibitors with Ki values of 0.87 and 3.12 μmol/L, respectively. Molecular docking experiments confirmed that the higher inhibitory potency of TTP and gAgAP might be attributed to the formation of several critical hydrogen bonds with the active site residues in ACE. We further demonstrated that TTP and gAgAP initiated a rapid and significant decrease in systolic blood pressure (SBP) in spontaneously hypertensive rats (SHRs). TTP treatment lowered SBP to the same extent as captopril, although the duration of anti-hypertensive effect was shorter in TTP group than that observed in captopril group. Moreover, the transcription levels of angiotensin II receptor type 1 (agtr1) and miR-132/-212 were downregulated in SHRs after administration of TTP and gAgAP. In particular, TTP treatment caused a comparable reduction of agtr1 levels compared to captopril treatment, while miR-132/212 expression was significantly decreased. These results showed that compound TTP might be served as a potential antihypertensive candidate.