Characterisation of novel angiotensin-I-converting enzyme inhibitory tripeptide,Gly-Val-Arg derived from mycelium of Pleurotus pulmonarius

It has been shown that fraction D₆ from Pleurotus pulmonarius has the potential to inhibit ACE. After this discovery, additional studies were conducted to obtain peptides from that fraction, as ACE inhibitors. By size exclusion chromatography, single peak was resolved and termed as Psec. The IC₅₀ of Psec was assessed to be 4.50 μg/mL, which was 2.5 times lower than that of D₆. When Psec was resolved by SDS-PAGE, three bands with estimated molecular weight of 63 kDa, 55 kDa and 11 kDa were observed. The protein bands were subjected to MALDI-Tof MS/MS for protein identification. By using the BIOPEP database for predicting in silico digestion of gastrointestinal (GI) enzymes, four stable tripeptides with ACE inhibitor potential resulting from GI enzyme digestion were identified, namely GVR, VVR, NPR, and VVL. The IC₅₀ was estimated to be 55 μg/mL, 93 μg/mL, 110 μg/mL and >250 μg/mL individually. Based on a Lineweaver-Burk plot, tripeptide GVR was determined to be a competitive inhibitor and this was confirmed by molecular docking analysis. At 100 mg/kg of body weight (bw), the tripeptide GVR reduced SBP 33.5 mm Hg in SHRs. The results suggested that this tripeptide is potentially beneficial as an antihypertensive agent.