Converting Enzyme Inhibitory Peptides Research Articles

Discovery of a novel nanomolar angiotensin-I converting enzyme inhibitory peptide with unusual binding mechanisms derived from Chlorella pyrenoidosa

Chlorella pyrenoidosa (C. pyrenoidosa) has been cultivated in large quantities, and was proven to be antihypertensive when consumed orally. However, the antihypertensive peptides derived from C. pyrenoidosa remains scarce. In this study, trypsin was chosen to prepare the hydrolysate of C. pyrenoidosa, which was then fractionated by column chromatography. And ninety-nine peptides were identified by LC-MS/MS, after which 10 peptides were chosen by docking-based virtual screening and demonstrated the ability to inhibit ACE. Among them, LVAKA (LV-5) had the lowest IC50 (26.66 μM). LV-5, LKKAP, and PGLRP were identified as non-competitive ACE inhibitory peptides that exhibited significant stability in the face of extreme pH and high temperatures. Insilico and in-vitro simulated gastrointestinal digestion revealed that these three peptides could release ACE inhibitory peptide fragments after digestion. The sequence optimization of LV-5 led to the identification of LRAKA (LR-5), which was recognized as a novel nanomolar ACE peptide with an IC50 of 350 nM in-vitro and a potent antihypertensive effect in-vivo. Moreover, molecular dynamic simulation indicated that LR-5 interacted with an unconventional binding site in ACE. These findings underscore the potential of Chlorella as a source of antihypertensive peptides and suggest a promising future for the use of Chlorella-derived peptides in the management of hypertension.

Angiotensin converting enzyme (ACE) inhibitory peptide from the tuna (Thunnus thynnus) muscle: Screening, interaction mechanism and stability

In this study, the purpose was to screen novel angiotensin converting enzyme inhibitory peptides (ACEIPs) from tuna muscle taking two-steps enzymatic hydrolysis (Neutrase and Alkaline). Following isolation and purification by ultrafiltration, the Sephadex G-15 gel chromatography and reversed-phase high-performance liquid chromatography based on active-guide, the amino acid sequence was identified using Q-Orbitrap-MS/MS. Five peptides were chose synthesized based on the in silico screening methods. Among these, the two novel ACEIPs LTGCP and YPKP showed better inhibitory ability, and their corresponding IC50 values were 64.3 μM and 139.6 μM. Subsequently, the interaction mechanism of the best active peptide (LTGCP) against ACE was investigated by inhibitory pattern, molecular docking and molecular dynamic simulation. The result displayed that LTGCP was a mix-type inhibitor against ACE from the Lineweaver-Burk plots. LTGCP formed seven hydrogen bonds based on the molecular docking and the binding energy was −7.29 kcal/mol. LTGCP formed a stability complex with ACE based on the molecular dynamic simulation. Besides, LTGCP exhibited good stability in various temperature, pH and gastrointestinal digestion. Finally, the 0.125 mM ∼ 1.0 mM LTGCP exhibited no-toxic for Caco-2 cell. In summary, these findings showed that tuna was a good material to prepare ACEIPs and LTGCP may be the good potential antihypertensive drug or nutraceuticals.

Preparation and Vasodilation Mechanism of Angiotensin-I-Converting Enzyme Inhibitory Peptide from Ulva prolifera Protein.

Ulva prolifera, a type of green algae that can be consumed, was utilized in the production of an angiotensin-I converting enzyme (ACE) inhibitory peptide. The protein from the algae was isolated and subsequently hydrolyzed using a neutral protease. The resulting hydrolysate underwent several processes including Sephadex-G100 filtration chromatography, ultrafiltration, HPLC-Q-TOF-MS analysis, ADMET screening, UV spectrum detection test, molecular docking, and molecular dynamic simulation. Then, the ACE inhibitory peptide named KAF (IC50, 0.63 ± 0.26 µM) was identified. The effectiveness of this peptide in inhibiting ACE can be primarily attributed to two conventional hydrogen bonds. Additionally, it could activate endothelial nitric oxide synthase (eNOS) activity to promote the generation of nitric oxide (NO). Additionally, KAF primarily increased the intracellular calcium (Ca2+) level by acting on L-type Ca2+ channel (LTCC) and the ryanodine receptor (RyR) in the endoplasmic reticulum, and completed the activation of eNOS under the mediation of protein kinase B (Akt) signaling pathway. Our study has confirmed that KAF has the potential to be processed into pharmaceutical candidate functions on vasoconstriction.

Angiotensin converting enzyme inhibitory hydrolysate and peptide fractions from chicken skin collagen, as modulators of lipid accumulation in adipocytes 3 T3-L1, after in vitro gastrointestinal digestion

Inhibitory activity against angiotensin-converting enzyme (IAACE) by chicken skin collagen hydrolysate (CSCH) and their peptide fractions before and after in-vitro gastrointestinal digestion, were evaluated; as well as their ability to modulate lipid accumulation in 3 T3-L1 adipocytes. Before digestion, peptide fraction <1 kDa (F4) showed the highest IAACE (p < 0.05) followed by CSCH. After these samples were digested, F4 presented an IAACE with IC50 similar to its digest (DF4) (188.84 and 220.03 μg/mL, respectively), which was 2-fold lower (p < 0.05) than IC50 of fraction <1 kDa from post-digested hydrolysate (FDH) (388.57 μg/mL). Nine peptides were identified as the potential ACE inhibitors in F4 and DF4. Addition of DF4 (800 μg/mL) reduced(p < 0.05) lipid accumulation by 83% within preadipocytes. A 45–60% reduction of lipid accumulation within differentiated adipocytes was obtained by adding FDH and DF4 (regardless the concentration). These results, digested CSCH and F4 with IAACE may be considered as potential adjuvants for obesity treatment.

Isolation and purification of angiotensin converting enzyme inhibitory peptide from goat milk hydrolysate by ultrafiltration membrane

Hypertension been a significant risk factor for cardiovascular illness. Synthesized angiotensin converting enzyme (ACE) inhibitors are active antihypertensive medicines they frequently generate unwanted side effects. This study describes the isolation and purification of an ACE inhibitory peptide from goat milk hydrolysate (Sahel breed). Hydrolysates containing angiotensin converting enzyme (ACE) inhibitory peptide were produced from goat milk by pepsin and trypsin. The strongest ACE inhibitory action was found in pepsin hydrolysate (57%) at 12h, hence was further purified. Purification was done using a 10 kDa ultrafiltration membrane and three steps of RP-HPLC to obtain ACE inhibitory peptide with activity of 84% and IC50 of 3.25±0.11 μg/ml. Lineweaver–Burks’ plots showed that the inhibitory kinetic mechanism of this peptide was competitive. In conclusion, ACE inhibitory peptide from goat milk hydrolysate treated with pepsin may be positive constituent to serve as drug against hypertension.

Angiotensin-I converting enzyme (ACE) inhibitory bioaccessible peptides obtained from protein extracts of Macrocystis pyrifera and Chondracanthus chamissoi seaweeds

Hypertension is a paramount chronic health concern, underscoring the critical need for preventive measures in public health. In recent years, research has discovered natural anti-hypertensive agents, including those derived from macroalgae. This study focuses on enzymatically hydrolyzing protein extracts from Macrocystis pyrifera and Chondracanthus chamissoi seaweeds to yield angiotensin I-converting enzyme (ACE) inhibitory peptides, potentially applicable in both food and bioactive products. ACE inhibitory activity was evaluated for enzymatic hydrolysates generated using bromelain, papain, and alcalase. Notably, hydrolysates produced using alcalase demonstrated the highest effect, yielding 74 % ACE inhibition for M. pyrifera and 58 % for C. chamissoi protein extracts. Optimization efforts focused on hydrolysis conditions, varying hydrolysis time and substrate-to-enzyme ratio, resulting in peak ACE inhibition of 79.9 % for M. pyrifera (5.3 h, 12.7 S:E ratio) and 70.3 % for C. chamissoi (6 h, 10 S:E ratio).Further analysis explored the relationship between molecular size separation and ACE inhibitory activity in algae hydrolysates. Fractionation via ultrafiltration revealed that fractions below 3 kDa exhibited the highest ACE inhibitory potency. Additionally, in vitro digestion studies employing pepsin and pancreatin treatments demonstrated the bioaccessibility of the seaweed-derived bioactive peptides, with maintained or enhanced bioactivity post-digestion. These findings underscore the potential of protease hydrolysates from M. pyrifera and C. chamissoi as sources of ACE inhibitory activity. Consequently, they present an exciting natural source of functional ingredients or nutraceuticals for hypertension management, with the benefits of easy implementation, profitability, and sustainability in their production process.

Purification of angiotensin converting enzyme inhibitory peptides and antihypertensive effect generated from Indonesian traditional fermented beef (Cangkuk).

Traditional fermented meat products can be considered a source of bioactive peptides. Cangkuk, a traditional Indonesian fermented beef product is one source of angiotensin converting enzyme (ACE) inhibitory peptides. This study aimed to identify ACE-inhibitory peptides from Cangkuk and analyze their antihypertensive effects. The water-soluble fraction of Cangkuk was fractionated to obtain ACE-inhibitory peptides using an ethanol solvent at several concentrations and solid-phase extraction with an OASIS HLB cartridge followed by purification with reversed-phase high-performance liquid chromatography (RP-HPLC). HPLC-MS was used to identify target peptides, followed by automatic protein sequencer analysis to detect peptide sequences. Antihypertensive effects were analyzed on the water-soluble fraction and synthesized peptides. The animal model comprised 14-16-week-old male spontaneously hypertensive rats (SHRs) (~320 g average body weight) with mean systolic blood pressures (SBPs) higher than 190 mmHg. All oral doses of peptides were 1 mL in volume. Distilled water was used as a control. The antihypertensive activities of the sample and control were observed by measuring the SBP at 0, 2, 4, 6, 8 and 24 h after oral administration. Two sequences of ACE inhibitory peptides were found, EAPLNPKANR (IC50 value of 44.6 μmol/L) and IVG (IC50 value of 97.3 μmol/L). The water-soluble fraction demonstrated an antihypertensive effect on SHRs after oral administration at 100 mg/kg body weight, maximally lowering the SBP by 14.9 mmHg 8 h after administration. The tripeptide IVG showed the highest reduction of SBP, 24.76±2.1 mmHg 8 h after administration. The decapeptide EAPLNPKANR showed the highest reduction of SBP, 21.0±1.9 mmHg, 8 h after administration. All the samples differed significantly from the control (p<0.01). Cangkuk has potential as a functional food ingredient acting as an antihypertensive agent.

STUDY OF ANGIOTENSIN-I CONVERTING ENZYME INHIBITORY PEPTIDES DERIVED FROM Ficus pumila var. awkeotsang SEEDS HYDROLYSATE

Hypertension also known as high blood pressure that has associated with multi-metabolic pathways such as the renin-angiotensin-aldosterone system (RAAS). There have been several synthetic ACE inhibitory drugs used clinically as therapeutics for hypertension. However, synthetic drugs showed side effects on human health after long-term use. Therefore, alternative natural ACE inhibitors from food-derived are necessary to develop. The study aimed to examine the activity of angiotensin-I converting enzyme inhibitory peptides derived from Ficus pumila var. awkeotsang seeds hydrolysate and to study the efficiency of enzymatic digestion. This study used four enzymes (trypsin, pepsin, thermolysin, and chymotrypsin) to release bioactive peptides from Ficus pumila var. awkeotsang seeds that could exhibit an antihypertensive effect. The results showed that Ficus pumila var. awkeotsang trypsin hydrolysate has the highest ACEI activity, 90.37%, and the IC50 reached 169±3.5 µg/mL. Then, the hydrolysate produced by trypsin has the highest degree of hydrolysis, 4%, after 8 hours of incubation. Hence, Ficus pumila var. awkeotsang seeds hydrolysate could develop as an alternative natural product that is responsible for ACE-inhibitory activity.

Impact of Lactiplantibacillus plantarum and casein fortification on angiotensin converting enzyme inhibitory peptides in yogurt: identification and in silico analysis.

In this study, the effects of Lactiplantibacillus plantarum M11 (Lb. plantarum M11) in conjunction with sodium caseinate on the characteristics and angiotensin converting enzyme (ACE) inhibitory activity of yogurt were investigated. ACE inhibitory peptides (ACEIPs) in yogurt were identified by nano-LC-MS/MS and potential ACEIPs were predicted by in silico and molecular docking methods. The results showed that the ACE-inhibitory activity of yogurt was significantly enhanced (p < 0.05), while maintaining the quality characteristics of the yogurt. Thirteen ACEIPs in the improved yogurt (883 + M11-CS group) were identified, which were more abundant than the other yogurt groups (control 883 group, 883 + M11 group and 883-CS group). Two novel peptides with potential ACE inhibitory activity, YPFPGPIH and NILRFF, were screened. The two peptides showed PeptideRanker scores above 0.8, small molecular weight and strong hydrophobicity, and were non-toxic after prediction. Molecular docking results showed that binding energies with ACE were -9.4 kcal mol-1 and -10.7 kcal mol-1, respectively, and could bind to the active site of ACE. These results indicated that yogurt with Lb. plantarum M11 and sodium caseinate has the potential to be utilized as a functional food with antihypertensive properties. The combination of ACEIP-producing strains and casein fortification could be an effective method to promote the release of ACEIPs from yogurt.

In Vitro Stability of ACE-Inhibitory Peptides of Rohu Fish Waste to Heat, pH and Gastrointestinal Enzymes

Angiotensin-I converting enzyme inhibitory (ACEi) peptides were prepared from rohu (Labeo rohita) fish wastes by enzymatic hydrolysis [1.1% alcalase concentration (v/w); 130 min time; 52°C temperature and 0.8:1 solid-liquid ratio]. Ultrasound Assisted Enzymatic Extraction (UAEE) and Microwave Assisted Enzymatic Extraction (MAEE) were performed to enhance degree of hydrolysis (DH), ACEi activity, and peptide yield (PY). The ACEi peptides were examined for stability during thermal processing, varied pH treatments and in vitro gastrointestinal digestion. Peptides were stable at different temperatures (25, 37, 55, 75, and 100°C) except at 121°C which reduced their stability by 7%, 6.9% and 2.2% in UAEE, MAEE and Non-Assisted Enzymatic Extraction (NAEE) peptides, respectively. Similarly, peptides retained ACEi at pH 2 to 8 and subsequent reduction at pH&gt;8. In vitro digestion studies showed stability of all peptides to GI digestion at 0.05% pepsin, 0.05% trypsin, 0.05% chymotrypsin and the combination of 0.025% trypsin and 0.025% chymotrypsin except MAEE peptides showing less stability with pepsin (0.05%). Therefore, it is concluded that these ACEi peptides derived from rohu fish waste, stable to heat, pH and gastrointestinal enzymatic action, can be used as ingredient in functional foods, which undergo thermal processing and digestion.

Characterization of novel angiotensin-I converting enzyme inhibitory peptides derived from Taiwan red quinoa (Chenopodium formosanum Koidz.) seed proteins using two sequential bioassay-guided fractionations

Characterization of novel angiotensin-I converting enzyme inhibitory peptides derived from Taiwan red quinoa (Chenopodium formosanum Koidz.) seed proteins using two sequential bioassay-guided fractionations

Study of screening, transport pathway, and vasodilation mechanisms on angiotensin-I converting enzyme inhibitory peptide from Ulva prolifera proteins

Study of screening, transport pathway, and vasodilation mechanisms on angiotensin-I converting enzyme inhibitory peptide from Ulva prolifera proteins

Screening, Characterization, and Mechanistic Evaluation of Angiotensin Converting Enzyme Inhibitory Peptides Derived from Milk Fermented with Lactobacillus delbrueckii QS306 with and without Ultrahigh-Pressure Treatment.

In this study, the peptides in milk fermented with Lactobacillus delbrueckii QS306 with and without ultrahigh-pressure treatment were identified using UPLC-Q-exactive-HF-X-MS/MS. In total, 27 novel pentapeptides with potential angiotensin converting enzyme inhibitory (ACEI) activity were screened via bioinformatic analysis, and the activities of seven novel pentapeptides were assessed. Among them, HLPLP, PYPQR, and VAPFP exhibited better IC50 values. Stability assessment via in vitro simulation revealed that the three pentapeptides were significantly reduced (P < 0.05) during digestion but exhibited 85% activity after digestion. HLPLP was a competitive inhibitor, while PYPQR and VAPFP were noncompetitive inhibitors of ACE. Molecular docking indicated that the three peptides could stably bind to ACE. Molecular dynamics (MD) simulation and activity verification indicated that PYPQR and VAPFP had better stability and activity. This study demonstrated that novel ACEI pentapeptides in milk fermented with L. delbrueckii QS306 with and without ultrahigh-pressure treatment could be considered promising candidates for controlling hypertension.

Identification of novel angiotensin converting enzyme (ACE) inhibitory peptides from Pacific saury: In vivo antihypertensive effect and transport route

Nature food-derived angiotensin converting enzyme inhibitory peptides (ACEIPs) can be potent and safe therapeutics for many medical illnesses, particularly hypertension. In this study, novel ACEIPs were screened and identified from Pacific saury by bio-activity guided approach through ultrafiltration membrane, Sephadex G-25 and RP-HPLC. The antihypertensive effect of ultrafiltration fraction was confirmed with spontaneous hypertensive rats' (SHRs) model. The peptides sequences of which gave the best activity was identified by Q-Orbitrap-MS/MS and selectively synthesized based on the binding energy of molecular docking. Five peptides VVLASLK, LTLK, LEPWR, ELPPK and LPTEK were synthesized, and the peptide LEPWR (IC50 = 99.5 μM) showed the best ACE inhibitory ability. Furthermore, LEPWR against ACE in a mixed competitive pattern and formed six hydrogen bonds with ACE. Additionally, the apparent permeability coefficient (Papp) of LEPWR was 3.56 ± 0.14 × 10−6 cm/s and paracellular transport across tight junctions was the main pathway across the Caco-2 monolayer. Therefore, the Pacific saury is a good material to prepare ACEIPs, but antihypertensive mechanism of peptide LEPWR on SHRs needs further investigation.

Identification and mechanistic study of four novel ACE inhibitory peptides from maize germ protein hydrolysates

Nowadays, much exertion has been given to identifying angiotensin-I converting enzyme inhibitory peptides (ACEIPs) from food by-products, while little attention has been paid to exploiting the potential use of maize germ proteins. Here, we identified four novel ACEIPs -PW, VTLL, LPGP, and SPGTAF, from maize germ protein hydrolysates. Inhibition assay demonstrated that these four peptides suppressed ACE activity with high potencies. Kinetics studies showed that PW inhibited ACE in a non-competitive manner with a Km of 1.15 mmol/L, whereas VTLL, LPGP, and SPGTAF were ACE substrate-competitive inhibitors with a constant Vmax of 0.005 △345 nm/min. Furthermore, molecular docking proved that PW mainly interacted with the key residues in the hydrophobic pocket of ACE through hydrogen bonding. Meanwhile, VTLL, LPGP, and SPGTAF docked at the catalytic domain of ACE and stabilized by hydrogen bonding with residues that coordinated Zn (II) or substrates. Our study suggests that the by-add product of maize could function as an alternative source for generating ACEIPs.

Structure identification and inhibitory mechanism evaluation of three novel angiotensin converting enzyme (ACE) inhibitory peptides from small-aroma chicken

Small-aroma chicken with a high protein content, is widely distributed in the mountainous area of Yunnan-Guizhou Plateau, China. In this work, three novel ACE-inhibitory peptides, Leu-Thr-Glu-Lys-Val-Val-Phe (LTQKVVF), Leu-Asp-Asp-His-Phe-Leu (LDDHFL), and Val-Pro-Gly-Pro-Glu-Pro-Lys-Pro (VPGPEPKP), were prepared from the Small-Aroma Chicken breast. The purification and identification protocol employed comprised ion-exchange chromatography, gel filtration chromatography, reverse phase-high performance liquid chromatography (RP-HPLC), and nano liquid chromatography-electrospray ionization–tandem mass (Nano-LC-ESI–MS/MS). Compared with VPGPEPKP and VPGPEPKP, LTQKVVF displayed noticeable ACE inhibitory activity, with IC50 values of 189.34 μM. What’s more, the Lineweaver-Burk plots revealed peptides LTQKVVF and LDDHFL acted as the mixed-competitive inhibitor while VPGPEPKP inhibited ACE in a manner similar to uncompetitive inhibition. The binding free energies of LTQKVVF, LDDHFL, and VPGPEPKP for ACE were −8.1 kcal/mol, −8.6 kcal/mol, and −9.6 kcal/mol, respectively. The strong inhibition of ACE by VPGPEPKP may be attributed to the interaction of hydrogen bonds, alkyl, and pi-alkyl, which formed by crucial residues of ACE.

Anchovy’s protein as a potential precursor of Angiotensin-I Converting Enzyme (ACE) inhibitory peptide and Dipeptidyl Peptidase-IV (DPP-IV) inhibitory peptide by an in silico approach

Protein from fish is known as the precursor of biologically active peptides that exert various health benefits such as antihypertensive, antitumor, and immunomodulatory properties. Hence, this study aimed to perform an extraction of anchovy, LC-MS/MS analysis and in silico evaluation of the major proteins in anchovies as potential precursors of biologically active peptides in addition to determining whether such peptides can be released by selected proteolytic enzymes. Anchovy was subjected to protein extraction followed by total soluble protein concentration determination using Bradford assay. The sample was subjected to in-solution trypsin digestion, which was then analysed by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS). A bioinformatic approach by PEAKS Studio was used to identify the protein. A total of four anchovy’s proteins which are myosin light chain 1, V(D)J recombination-activating protein, 60 kDa chaperonin and heat shock protein 90AA1 were identified. Then, the identified proteins were subjected to in silico approach using the BIOPEP database. The biological potential of the theoretically released angiotensin-I converting enzyme (ACE) inhibitory peptides and dipeptidyl peptidase (DPP)-IV inhibitory peptides were predicted by determining the frequency of occurrence of fragments with a given activity. 60 kDa chaperonin and heat shock protein 90AA1 predicted the highest number of biological activities for ACE inhibitory peptides (284 and 264 fragments) and DPP-IV inhibitory peptides (395 and 409 fragments). The most promising enzyme for the generation of bioactive peptides from anchovy protein was anticipated to be pepsin (pH &gt; 2), which theoretically released a high number of DPP-IV inhibitory peptides and ACE inhibitory peptides through the action of in silico proteolysis. Overall, this work highlighted that anchovy protein could be a promising precursor of bioactive peptides that have ACE and DPP-IV inhibitory activities for developing functional food or nutraceutical products.

Purification and molecular docking of angiotensin converting enzyme-inhibitory peptides derived from corn gluten meal hydrolysate and from in silico gastrointestinal digestion

Corn gluten meal (CGM) was hydrolyzed by Alcalase with the degree of hydrolysis (DH) and protein recovery of 28.7 % and 67.7 %, respectively. Ultrafiltration revealed that the 3–10 kDa fraction (IC50 =15.98 µg/mL) involved potent ACE inhibitory peptides. The peptides in the fraction were further separated by size exclusion chromatography and reverse-phase chromatography. The novel peptide DLLGCS was identified to be the most active ACE inhibitor (IC50 =39.0 μM). The in silico digested peptide CS was approximately 4.5 times higher than its parent counterpart (IC50 =8.5 µM). Peptides CS and DLLGCS showed an uncompetitive inhibitor characteristic with Ki values of 12.52 and 11.40 µM, respectively. Based on molecular docking, both peptides interacted with the nonactive site of ACE, primarily via hydrogen bonds at Arg522, Asp121, Glu123 and Lys118 residues for DLLCGS and Glu162, Ser147 and Glu349 residues for CS. Therefore, peptides originated from CGM hydrolysates could exhibit a higher degree of inhibition against ACE enzyme upon gastrointestinal digestion, which is likely to be a potential source of bioactive peptides with ACE inhibitory activity.

Preparation and activity evaluation of angiotensin-I converting enzyme inhibitory peptides from protein hydrolysate of mulberry leaf.

Angiotensin-I converting enzyme (ACE) inhibitory peptides drew wide attention in the food industry because of their natural reliability, non-toxicity, and safety. However, the characteristics of ACE inhibitory peptides obtained from protein hydrolysate of mulberry leaf prepared by Flavourzyme were still unclear. Based on the single-factor test, the Plackett-Burman test and response surface test were used to determine the key factors affecting the ACE inhibition rate in mulberry leaf protein hydrolysate and the optimum conditions of enzymatic hydrolysis. The results showed that the optimum technical parameters were as follows: the ratio of material to liquid is 1: 25 (w / v, g/mL), the Flavourzyme to substrate ratio was 3,000 U/g, the temperature of enzymatic hydrolysis was 50°C, pH was 6.3, and the time of enzymatic hydrolysis was 2.9 h. The ACE inhibitory peptides in the mulberry leaf protein hydrolysates were purified by ultrafiltration and gel filtration, aiming to obtain the highest active component. The 12 peptide sequences were identified by reverse liquid chromatography-mass spectrometry, and then, they were docked to the crystal structure of human angiotensin-I converting enzyme (1O8A), and the interaction mechanisms of 12 peptide sequences and 1O8A were analyzed. The docking results showed that among the 12 peptide sequences, ERFNVE (792.37 Da), TELVLK (351.72 Da), MELVLK (366.72 Da), and FDDKLD (376.67 Da), all had the lowest docking energy, and inhibition constant. The chemosynthetic ERFNVE (IC50: 2.65 mg/mL), TELVLK (IC50: 0.98 mg/mL), MELVLK (IC50:1.90 mg/mL) and FDDKLD (IC50:0.70 mg/mL) demonstrated high ACE-inhibitory activity with competitive inhibition mode. These results indicated that the ACE-inhibiting peptides from mulberry leaf protein hydrolyzed (FHMP) had the potential activities to inhibit ACE and could be used as functional food or drugs to inhibit ACE. This work provides positive support for mining the biological activity of mulberry leaves in the treatment of hypertension.

Molecular docking and antihypertensive effects of a novel angiotensin-I converting enzyme inhibitory peptide from yak bone.

A novel angiotensin-converting enzyme (ACE) inhibitory peptide ser-ala-ser-val-ile-pro-val-ser-ala-val-arg-ala (SASVIPVSAVRA) was purified and identified from yak bone by Electrospray Ionization-Time of Flight-Mass Spectrometry (ESI-TOF-MS). Results in vitro showed that the peptide exhibited strong ACE inhibition activities with an IC50 of 54.22 μM. Molecular docking results showed the binding between the peptide SASVIPVSAVRA and ACE mainly driven by van der Waals forces, hydrogen bonds and metal receptor. Interestingly, the ACE inhibition activities of the peptide increased about 19% after digestion, but none of its metabolites showed stronger activity than it. The in vivo experiment showed that the antihypertensive effect of peptide SASVIPVSAVRA at dose of 30 mg/kg is nearly equal to Captopril at dose of 10 mg/kg to spontaneously hypertensive rats (SHRs). The antihypertensive effect mechanism of SASVIPVSAVRA should be further studied through plasma metabolomics and bioanalysis. Structure analysis of amino acids and peptides produced during digestion may help better understand the antihypertensive effect of peptides.