Identification and in silico characterization of a novel peptide inhibitor of angiotensin converting enzyme from pigeon pea (Cajanus cajan)

Background: Plants are important sources of bioactive peptides. Among these, angiotensin converting enzyme (ACE) inhibitory peptides have a major focus on their ability to prevent hypertension. Inhibition of ACE has been established as an effective approach for the treatment of ACE associated diseases. Hypothesis/purpose: Some synthetic ACE inhibitory drugs cause side effects and hence there is a constant interest in natural compounds as alternatives. Study design: The study was designed to identify and characterize a peptide molecule from pigeon pea which has the biological property to inhibit ACE and can be developed as a therapeutic approach towards hypertension. Methods: Seeds of pigeon pea (Cajanus cajan (L.) Millsp.) was fermented with Aspergillus niger, a proteolytic fungus isolated from spoiled milk sweet. The extract was purified by size exclusion chromatography by FPLC system. The fractions that showed ACE inhibition was subjected to LC-MS/MS for sequence identification. The stability of the peptide was analyzed by molecular dynamic simulations and the interaction sites with ACE were identified by molecular docking. Results: The study report a novel ACE inhibitory octapeptide Val-Val-Ser-Leu-Ser-Ile-Pro-Arg with a molecular mass of 869.53 Da. The Lineweaver-Burk plot indicated that the inhibition of ACE by this peptide is in competitive mode. Also, molecular docking and simulation studies showed a strong and stable interaction of the peptide with ACE. Conclusion: The results clearly show the inhibitory property of the peptide against ACE and hence it can be explored as a therapeutic strategy towards hypertension and other ACE associated diseases.