Exploration of inhibitor effect of Gly-Pro (GP), Arg-Gly-Asp-Ser (RGDS) and Ser-Asp-Gly-Arg-Gly (SDGRG) bioactive peptides on angiotensin-converting enzyme activity purified from human serum.

Abstract

Bioactive peptides (BPs) are a natural and important alternative to synthetic angiotensin-converting enzyme (ACE) inhibitors used in the treatment of hypertension. In this study, ACE was 3575-fold purified from human serum with the affinity chromatography process in one step. The molecular weight and purity of ACE were identified using the SDS-PAGE process and seen in two bands at around 60 kDa and 70 kDa on the gel. V_max and K_M values from the Lineweaver-Burk graphic were determined as 96.15 (µmol/min) mL^-1 and 0.2 mM, respectively. The effects of Gly-Pro (GP), Arg-Gly-Asp-Ser (RGDS) and Ser-Asp-Gly-Arg-Gly (SDGRG) BPs on purified ACE were researched. Also, lisinopril was used as a reference inhibitor. GP, RGDS and SDGRG on purified ACE demonstrated an inhibitory effect. IC₅₀ values for these peptides were found as 184.71, 107.16 and 32.54 µM, respectively. K_i values and type of inhibitory for GP, RGDS and SDGRG by the Lineweaver-Burk chart were found. The type of inhibitory for these peptides was calculated as reversible-competitive inhibitory. K_i values for GP, RGDS and SDGRG were calculated to be 260.02, 63.44 and 11.42 µM, respectively. Also, the SDGRG indicated a higher inhibition effect on ACE activity than the GP and RGDS. The IC₅₀ value of lisinopril was designated as 0.35 nM. The inhibition type of lisinopril was designated as reversible noncompetitive inhibition from the Lineweaver-Burk chart and the K_i value was 0.15 nM. Herein, it was concluded that GP, RGDS and SDGRG have ACE inhibitor potential.