The angiotensin I-converting enzyme (ACE) plays a crucial role in regulating blood pressure and its inhibition is considered a treatment for hypertension. Cys-Met-Try-Leu-Ala-Ser-Gly (CMYLASG), a heptapeptide derived from Gnetum gnemon L. seeds, is an ACE-inhibitory peptide. This study aimed to investigate the expression of the tandem repeat heptapeptide gene (Gg-7pAH) and its ACE-inhibitory activity. The heptapeptide gene was cloned and expressed into the pBT7–N–His vector and synthesized as the recombinant protein Gg-7pAH. Sequencing results of the recombinant plasmid showed high similarity with the sequence of the heptapeptide genes inserted. The recombinant protein was expressed mostly as a soluble protein in Escherichia coli BL21 after 8 h of induction using isopropyl-β-D-thiogalactoside (IPTG) at room temperature around 26-28 ºC. Purification was achieved using Ni2+-chelate (Ni-NTA) affinity chromatography, which produced a 12 kDa recombinant protein. Hydrolysis of the recombinant protein with 2% formic acid released the heptapeptide as a target molecule. The hydrolyzed recombinant protein exhibited excellent ACE-inhibitory activity with an IC50 of 8.64 μM, which was lower than that of captopril (IC50 = 11.68 μM). Inhibitory kinetics showed that the heptapeptide was a non-competitive inhibitor of ACE and functioned suitably at low substrate concentrations. These findings revealed the high potency of the recombinant Gg-7pAH to produce ACE-inhibitory peptides that may be used as hypotensive agents and nutraceuticals for hypertension treatment.
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