Inhibition effect of Gly-Arg-Gly-Asp-Ser (GRGDS) and Arg-Gly-Asp (RGD) Bioactive Peptides on Angiotensin-Converting Enzyme Activity Purified from Human Serum

Angiotensin-converting enzyme (ACE, EC 3.4.15.1) is a physiological target for researching new antihypertensive drugs, as it is a substantial enzyme in the regulation of blood pressure. Herein, ACE was purified from human serum with affinity chromatography. Vmax and KM values were found as 60.98 (µmol/min)/mL and 0.34 mM, respectively. The effects of Gly-Arg-Gly-Asp-Ser (GRGDS) and Arg-Gly-Asp (RGD) bioactive peptides on purified ACE were researched. Also, captopril, a specific ACE inhibitory, was used as a reference inhibitor. Bioactive peptides, GRGDS and RGD, demonstrated the inhibitory effect on purified ACE with IC50 values of 46.39 µM and 456.46 µM, respectively. Ki values and kind of inhibition for GRGDS and RGD by the Lineweaver-Burk chart were found. The kind of inhibitory for these bioactive peptides was calculated as reversible-competitive inhibitory. Ki values for GRGDS and RGD were obtained as 93.28 µM and 435.67 µM, respectively. The IC50 value of captopril was designated as 1.57 nM. The inhibitory kind of captopril was designated as reversible non-competitive inhibitory and the Ki value was 0.99 nM. In this study, it was concluded that RGD and GRGDS bioactive peptides have the potential to be utilized as ACE inhibitors.