In silico analysis and molecular docking study of angiotensin I-converting enzyme inhibitory peptides from smooth-hound viscera protein hydrolysates fractionated by ultrafiltration

Revealing the ACE receptor binding properties and interaction mechanisms of salty oligopeptides from Stropharia rugosoannulata mushroom by molecular simulation and antihypertensive evaluation

The salty oligopeptides from Stropharia rugosoannulata have been proven to be potential ACE inhibitors. To investigate the ACE receptor binding properties and interaction mechanisms of salty oligopeptides, the molecular interaction, dynamics simulation, and antihypertensive evaluation cross-validation strategy were employed to reveal the oligopeptides' binding reactions and modes with the ACE receptor. Single oligopeptide (ESPERPFL, KSWDDFFTR) had exothermic and specific binding reactions with the ACE receptor, driven by hydrogen bonds and van der Waals forces. The coexistence of the multiple oligopeptide molecules did not produce the apparent ACE receptor competition binding reactions. The molecular dynamics simulation verified that the two oligopeptides disturbed the ACE receptor's different residue regions. Both oligopeptides could form stable complexes with the ACE receptor. Based on the classification of 50 oligopeptides' binding modes, ESPERPFL and KSWDDFFTR belonged to different classes, and their receptor binding modes and sites complemented, resulting in a potential synergistic effect on ACE inhibition. The antihypertensive effect of KSWDDFFTR and its distribution in the body were evaluated using SHR rats orally and ICR mice by tail vein injection, and KSWDDFFTR had antihypertensive effects within 8 h. The study provides a theoretical basis for understanding salty oligopeptides' ACE receptor binding mechanism and their antihypertensive effects.

Identification, structural characterization, and molecular dynamic simulation of ACE inhibitory peptides in whey hydrolysates from Chinese Rushan cheese by-product

To realize the high-value utilization of Rushan cheese by-product, Rushan cheese whey was used as a raw material to prepare angiotensin-Ⅰ-converting enzyme inhibitory peptides (ACEIPs). After enzymatic hydrolysisn and ultrafiltration, the sequences of peptides were identified by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS). Two novel ACE inhibitory peptides Phe-Asp-Arg-Pro-Phe-Leu (FDRPFL) and Lys-Trp-Glu-Lys-Pro-Phe (KWEKPF) were identified. Additionally, both of the peptides exhibited good water-solubility and no toxicity according to in-silico prediction. Fourier transform infrared spectroscopy results show that both FDRPFL and KWEKPF were enriched in β-turn and β-sheet structures. Lineweaver-Burk plots revealed that FDRPFL and KWEKPF exhibited non-competitive and mixed inhibition patterns, respectively. Molecular docking and MD simulation showed that hydrogen bonds and ionic bonds forces allowed FDRPFL and KWEKPF to form stable and compact complexes with ACE. In conclusion, enzymatic hydrolysis of Rushan cheese by-products yields bioactive peptides, increases the added value of whey and reduces environmental pollution.

A novel angiotensin-converting enzyme (ACE) inhibitory peptide from tilapia skin: Preparation, identification and its potential antihypertensive mechanism

To obtain food-derived peptides with high ACE inhibitory activity, tilapia skin was pretreated with steam explosion prior to enzymatic hydrolysis. The results showed that steam explosion pretreatment improved the hydrolysis efficiency and ACE inhibitory activity of fish skin hydrolysates. A novel ACE inhibitory peptide VGLFPSRSF (1009.17 Da) was obtained from steam-exploded fish skin hydrolysates. VGLFPSRSF had an IC50 value of 61.43 μM for ACE inhibitory activity, showing a non-competitive binding mode and gastrointestinal enzyme hydrolysis resistance. Molecular docking results showed that VGLFPSRSF interacted with ACE receptor protein through hydrogen bonding and hydrophobic interactions. Based on the results of network pharmacological analysis and molecular docking, VGLFPSRSF might regulate blood pressure through interaction with hypertensive targets such as AKT1, ACE, CD4, REN, and MMP9. Steam-exploded tilapia skin peptides had potential antihypertension activity and might be promising to achieve high-value utilization of fish skin by-products.

Selection of goat β-casein derived ACE-inhibitory peptide SQPK and insights into its effect and regulatory mechanism on the function of endothelial cells

The angiotensin I-converting enzyme (ACE)-inhibitory peptide SQPK was selected by in silico digestion and virtual screening from goat β-casein, and its effect and regulatory mechanism on function of endothelial cells was further evaluated. The results showed that SQPK exhibited relatively good ACE inhibition capacity (IC50 = 452.7 μg/mL). Treatment with 25 μg/mL SQPK for 12 h significantly elevated nitric oxide (NO) production, stimulated eNOS expression (p < 0.05) and affected the transcriptomic profiling of EA. Hy926 cells. In particular, SQPK stimulated the expression of genes encoding inflammatory cytokines (CXCL1/2 and IL6) but depressed encoding mesenchymal markers (FN1 and CNN3). Furthermore, SQPK modified the expression of genes involved in endothelial-to-mesenchymal transition (EndMT). Therefore, the selected peptide SQPK may exert potential protective effects on the function of endothelial cells by inhibiting the EndMT.

SlbHLH22-Induced Hypertrophy Development Is Related to the Salt Stress Response of the GTgamma Gene in Tomatoes

Hypertrophy development induced by the overexpression of SlbHLH22 (also called SlUPA-like) was susceptible to Xanthomonas in tomatoes. Transcriptome and metabolome analyses were performed on the hypertrophy leaves of a SlbHLH22-overexpressed line (OE) and wild type (WT) to investigate the molecular mechanism. Metabolome analysis revealed that six key metabolites were over-accumulated in the OE, including Acetylserine/O-Acetyl-L-serine, Glucono-1,5-lactone, Gluconate, 2-Oxoglutarate, and Loganate, implying that the OE plants increased salt or oxidant resistance under normal growth conditions. The RNA-seq analysis showed the changed expressions of downstream genes involved in high-energy consumption, photosynthesis, and transcription regulation in OE lines, and we hypothesized that these biological processes were related to the GTgamma subfamily of trihelix factors. The RT-PCR results showed that the expressions of the GTgamma genes in tomatoes, i.e., SlGT-7 and SlGT-36, were suppressed in the hypertrophy development. The expression of the GTgamma gene was downregulated by salinity, indicating a coordinated role of GTgamma in hypertrophy development and salt stress. Further research showed that both SlGT-7 and SlGT-36 were highly expressed in leaves and could be significantly induced by abscisic acid (ABA). The GTgamma protein had a putative phosphorylation site at S96. These results suggested GTgamma's role in hypertrophy development by increasing the salt resistance.

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.

Inhibition mechanism of membrane-separated silver carp hydrolysates on ice crystal growth obtained through experiments and molecular dynamics simulation

The membrane-separated silver carp hydrolysates (>10 k_D, 3-10 k_D and < 3 k_D) displayed abilities to mitigate oxidation and denaturation of myofibrillar protein and cryoprotective activities for frozen surimi. However, the mechanism of the membrane-separated fractions on ice crystal growth in the system is still unknown. Therefore, the cryoprotective activities (recrystallization inhibition, RI and thermal hysteresis activity, THA) of the fractions were investigated and the mechanism was explored by molecular dynamics (MD) simulation to predict the probable binding sites and model the possible interactions between the peptides and water/ice. The fractions < 3 k_D displayed remarkable RI activity, with significantly higher THA (0.60 ± 0.13 °C) and lower amount of ice nuclei (4.74 ± 0.53%) than that of fractions > 10 k_D and 3-10 k_D. The results of MD simulation certified that the main peptides in the fractions < 3 k_D interacted firmly with water molecules and inhibited growth of ice crystals with mechanism compatible with Kelvin effect. Hydrophilic and hydrophobic amino acid residues in the membrane-separated fractions offered synergistic effects on the inhibition of ice crystals.

Production, identification, in silico analysis, and cytoprotection on H2O2-induced HUVECs of novel angiotensin-I-converting enzyme inhibitory peptides from Skipjack tuna roes

Background

Exceeding 50% tuna catches are regarded as byproducts in the production of cans. Given the high amount of tuna byproducts and their environmental effects induced by disposal and elimination, the valorization of nutritional ingredients from these by-products receives increasing attention.

Objective

This study was to identify the angiotensin-I-converting enzyme (ACE) inhibitory (ACEi) peptides from roe hydrolysate of Skipjack tuna (Katsuwonus pelamis) and evaluate their protection functions on H₂O₂-induced human umbilical vein endothelial cells (HUVECs).

Methods

Protein hydrolysate of tuna roes with high ACEi activity was prepared using flavourzyme, and ACEi peptides were isolated from the roe hydrolysate using ultrafiltration and chromatography methods and identified by ESI/MS and Procise Protein/Peptide Sequencer for the N-terminal amino acid sequence. The activity and mechanism of action of isolated ACEi peptides were investigated through molecular docking and cellular experiments.

Results

Four ACEi peptides were identified as WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12), respectively. The affinity of WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12) with ACE was -8.590, -9.703, -9.325, and -8.036 kcal/mol, respectively. The molecular docking experiment elucidated that the significant ACEi ability of WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12) was mostly owed to their tight bond with ACE's active sites/pockets via hydrophobic interaction, electrostatic force and hydrogen bonding. Additionally, WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12) could dramatically elevate the Nitric Oxide (NO) production and bring down endothelin-1 (ET-1) secretion in HUVECs, but also abolish the opposite impact of norepinephrine (0.5 μM) on the production of NO and ET-1. Moreover, WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12) could lower the oxidative damage and apoptosis rate of H₂O₂-induced HUVECs, and the mechanism indicated that they could increase the content of NO and activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) to decrease the generation of reactive oxygen species (ROS) and malondialdehyde (MDA).

Conclusion

WGESF (TRP3), IKSW (TRP6), YSHM (TRP9), and WSPGF (TRP12) are beneficial ingredients for healthy products ameliorating hypertension and cardiovascular diseases.

Is It Still Relevant to Discover New ACE Inhibitors from Natural Products? YES, but Only with Comprehensive Approaches to Address the Patients' Real Problems: Chronic Dry Cough and Angioedema

Despite many publications related to the identification of new angiotensin-I-converting enzyme (ACE) inhibitors, especially peptides from natural products, the actual reason/s for why new ACE inhibitors need to be discovered are yet to be fully understood. New ACE inhibitors are pivotal to address serious side effects caused by commercially available ACE inhibitors in hypertensive patients. Despite the effectiveness of commercial ACE inhibitors, due to these side effects, doctors often prescribe angiotensin receptor blockers (ARBs). Recent evidence has shown the benefits of ACE inhibitors over ARBs in hypertensive patients and hypertensive-diabetes mellitus patients. In order to address these side effects, the somatic ACE's enzyme structures need to be revisited. The peptides isolated from the natural products need to be verified for their stability against ACE and several important gastrointestinal enzymes. The stable peptides sequence with the presence of favourable ACE inhibitory-related amino-acids, such as tryptophan (W), at the C-terminal need to be subjected to molecular docking and dynamics analyses for selecting ACE inhibitory peptide/s with C-domain-specific inhibition instead of both C- and N-domains' inhibition. This strategy will help to reduce the accumulation of bradykinin, the driving factor behind the formation of the side effects.

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.

Isolation and identification of antioxidative peptides from crocodile meat hydrolysates using silica gel chromatography

Crocodiles are cultured in large numbers in Asia and other places in order to protect wild resources and meet the needs of human life. In this study, crocodile (Crocodylus siamensis) meat proteins were extracted and hydrolyzed into peptides, their antioxidant peptides were isolated and purified by silica gel chromatography and identified by LC/MS. Crocodile meat proteins were optimally extracted with water and hydrolyzed by papain based on the degree of hydrolysis and antioxidant activity. The hydrolysates were fractionated by ultrafiltration into 3 kDa, 3–30 kDa, and ≥ 30 kDa fractions. The 3 kDa fraction showed most antioxidant activity of the hydrolysates. Its active peptides were separated by silica gel column chromatography and purified by silica gel TLC, based on TLC bio-autographic assays of the activity. Four highly active peptides were identified by LC/MS as SSLTIQFVEGQFVDSYDPTIENTFTK, VPPHIY, VAPEEHPVLLTEAPLNPK, and RNGLPGPIGPAG. The identified peptides were synthesized and showed 50% free radical scavenging activities at 1.0 mg/mL, equal or higher to ascorbic acid at 0.5 mg/mL, in both DPPH and ABTS assays. The results indicated that the 3 kDa hydrolyzed peptides of crocodile meat had high antioxidant activity and the active peptides can be effectively separated and purified by silica gel column chromatography and TLC.

Corn distillers solubles as a novel bioresource of bioactive peptides with ACE and DPP IV inhibition activity: characterization, in silico evaluation, and molecular docking

This study aimed to investigate the biological potential of underutilized and low-value corn distillers solubles, containing a unique unexplored blend of heat-treated corn and yeast proteins, from the bioethanol industries, by bioinformatic and biochemical approaches. Protein hydrolysates were produced by applying four commercially accessible proteases, among which alcalase provided the best results in terms of yield, degree of hydrolysis, molecular weight, number of proteins, bioactive peptides, and deactivation against anti-angiotensin I-converting enzyme (ACE) and anti-dipeptidyl peptidase IV (DPP IV). The optimal conditions to produce anti-ACE and anti-DPP IV peptides were using alcalase for 10.82 h and an enzyme : substrate ratio of 7.90 (%w/w), with inhibition values for ACE and DPP IV of 98.76 ± 1.28% and 34.99 ± 1.44%, respectively. Corn (α-zein) and yeast (glyceraldehyde-3-phosphate dehydrogenase) proteins were mainly suitable, upon enzymolysis, for the release of bioactive peptides. The peptides DPANLPWG, FDFFDNIN, WNGPPGVF, and TPPFHLPPP inhibited ACE more effectively as verified with binding energies of -11.3, -11.6, -10.5, and -11.6 kcal mol^-1, respectively, as compared to captopril (-6.38 kcal mol^-1). Compared with the binding energy of sitagliptin (-8.6 kcal mol^-1), WNGPPGVF (-9.6 kcal mol^-1), WPLPPFG (-9.8 kcal mol^-1), LPPYLPS (-9.7 kcal mol^-1), TPPFHLPPP (-10.1 kcal mol^-1), and DPANLPWG peptides (-10.1 kcal mol^-1) had greater inhibition potential against DPP IV. The peptides impeded ACE and DPP IV majorly via hydrophobic and hydrogen linkage interactions. The key amino acids TYR⁵²³, GLU³⁸⁴, and HIS³⁵³ were bound to the catalytic sites of ACE and GLN⁵⁵³, GLU²⁰⁶, PHE³⁶⁴, VAL³⁰³, and THR³⁰⁴ were bound to the DPP IV enzyme. The PHs can be used as ingredients in the feed or food industries with possible health advantages.

Novel angiotensin-converting enzyme inhibitory peptides from tuna byproducts—milts: Preparation, characterization, molecular docking study, and antioxidant function on H2O2-damaged human umbilical vein endothelial cells

To prepare peptides with high angiotensin-converting enzyme (ACE) inhibitory (ACEi) activity, Alcalase was screened from five proteases and employed to prepare protein hydrolysate (TMH) of skipjack tuna (Katsuwonus pelamis) milts. Subsequently, 10 novel ACEi peptides were isolated from the high-ACEi activity TMH and identified as Tyr-Asp-Asp (YDD), Thr-Arg-Glu (TRE), Arg-Asp-Tyr (RDY), Thr-Glu-Arg-Met (TERM), Asp-Arg-Arg-Tyr-Gly (DRRYG), Ile-Cys-Tyr (ICY), Leu-Ser-Phe-Arg (LSFR), Gly-Val-Arg-Phe (GVRF), Lys-Leu-Tyr-Ala-Leu-Phe (KLYALF), and Ile-Tyr-Ser-Pro (IYSP) with molecular weights of 411.35, 404.41, 452.45, 535.60, 665.69, 397.48, 521.61, 477.55, 753.91, and 478.53 Da, respectively. Among them, the IC₅₀ values of ICY, LSFR, and IYSP on ACE were 0.48, 0.59, and 0.76 mg/mL, respectively. The significant ACEi activity of ICY, LSFR, and IYSP with affinities of −7.0, −8.5, and −8.3 kcal/mol mainly attributed to effectively combining with the ACEi active sites through hydrogen bonding, electrostatic force, and hydrophobic interaction. Moreover, ICY, LSFR, and IYSP could positively influence the production of nitric oxide (NO) and endothelin-1 (ET-1) secretion in human umbilical vein endothelial cells (HUVECs) and weaken the adverse impact of norepinephrine (NE) on the production of NO and ET-1. In addition, ICY, LSFR, and IYSP could provide significant protection to HUVECs against H₂O₂ damage by increasing antioxidase levels to decrease the contents of reactive oxide species and malondialdehyde. Therefore, the ACEi peptides of ICY, LSFR, and IYSP are beneficial functional molecules for healthy foods against hypertension and cardiovascular diseases.

Purification and Identification of a Novel Angiotensin Converting Enzyme Inhibitory Peptide from the Enzymatic Hydrolysate of Lepidotrigla microptera

In this study, Lepidotrigla microptera were hydrolyzed with four different proteolytic enzymes (Papain, neutrase, flavourzyme, and alcalase), and their distribution of molecular weights and ACE-inhibitory activity were tested. The alcalase hydrolysates showed the maximum ACE-inhibitory activity. A novel ACE-inhibitory peptide was isolated and purified from Lepidotrigla microptera protein hydrolysate (LMPH) using ultrafiltration, gel filtration chromatography, and preparative high performance liquid chromatography (prep-HPLC). The amino acid sequence of the purified peptide was identified as Phe-Leu-Thr-Ala-Gly-Leu-Leu-Asp (DLTAGLLE), and the IC50 value was 0.13 mg/mL. The ACE-inhibitory activity of DLTAGLLE was stable across a range of temperatures (<100 °C) and pH values (3.0−11.0) and retained after gastrointestinal digestion. DLTAGLLE was further identified as a noncompetitive inhibitor by Lineweaver−Burk plot. The molecular docking simulation showed that DLTAGLLE showed a high binding affinity with ACE sites by seven short hydrogen bonds. As the first reported antihypertensive peptide extracted from alcalase hydrolysate of Lepidotrigla microptera, DLTAGLLE has the potential to develop functional food or novel ACE-inhibitor drugs.

Preparation, Characterization, and Cytoprotective Effects on HUVECs of Fourteen Novel Angiotensin-I-Converting Enzyme Inhibitory Peptides From Protein Hydrolysate of Tuna Processing By-Products

To effectively utilize skipjack tuna (Katsuwonus pelamis) processing by-products to prepare peptides with high angiotensin-I-converting enzyme (ACE) inhibitory (ACEi) activity, Neutrase was selected from five kinds of protease for hydrolyzing skipjack tuna dark muscle, and its best hydrolysis conditions were optimized as enzyme dose of 1.6%, pH 6.7, and temperature of 50°C using single factor and response surface experiments. Subsequently, 14 novel ACEi peptides were prepared from the high ACEi protein hydrolysate and identified as TE, AG, MWN, MEKS, VK, MQR, MKKS, VKRT, IPK, YNY, LPRS, FEK, IRR, and WERGE. MWN, MEKS, MKKS, and LPRS displayed significantly ACEi activity with IC₅₀ values of 0.328 ± 0.035, 0.527 ± 0.030, 0.269 ± 0.006, and 0.495 ± 0.024 mg/mL, respectively. Furthermore, LPRS showed the highest increasing ability on nitric oxide (NO) production among four ACEi peptides combining the direct increase and reversing the negative influence of norepinephrine (NE), and MKKS showed the highest ability on directly decreasing and reversing the side effects of NE on the secretion level of endothelin-1 (ET-1) among four ACEi peptides. These findings demonstrate that seafood by-product proteins are potential ACEi peptide sources and prepared ACEi peptides from skipjack tuna dark muscle, which are beneficial components for functional food against hypertension and cardiovascular diseases.

Preparation, Identification, Molecular Docking Study and Protective Function on HUVECs of Novel ACE Inhibitory Peptides from Protein Hydrolysate of Skipjack Tuna Muscle

To prepare bioactive peptides with high angiotensin-I-converting enzyme (ACE)-inhibitory (ACEi) activity, Alcalase was selected from five kinds of protease for hydrolyzing Skipjack tuna (Katsuwonus pelamis) muscle, and its best hydrolysis conditions were optimized using single factor and response surface experiments. Then, the high ACEi protein hydrolysate (TMPH) of skipjack tuna muscle was prepared using Alcalase under the optimum conditions of enzyme dose 2.3%, enzymolysis temperature 56.2 °C, and pH 9.4, and its ACEi activity reached 72.71% at 1.0 mg/mL. Subsequently, six novel ACEi peptides were prepared from TMPH using ultrafiltration and chromatography methods and were identified as Ser-Pro (SP), Val-Asp-Arg-Tyr-Phe (VDRYF), Val-His-Gly-Val-Val (VHGVV), Tyr-Glu (YE), Phe-Glu-Met (FEM), and Phe-Trp-Arg-Val (FWRV), with molecular weights of 202.3, 698.9, 509.7, 310.4, 425.6, and 606.8 Da, respectively. SP and VDRYF displayed noticeable ACEi activity, with IC₅₀ values of 0.06 ± 0.01 and 0.28 ± 0.03 mg/mL, respectively. Molecular docking analysis illustrated that the high ACEi activity of SP and VDRYF was attributed to effective interaction with the active sites/pockets of ACE by hydrogen bonding, electrostatic force, and hydrophobic interaction. Furthermore, SP and VDRYF could significantly up-regulate nitric oxide (NO) production and down-regulate endothelin-1 (ET-1) secretion in HUVECs after 24 h treatment, but also abolish the negative effect of 0.5 μM norepinephrine (NE) on the generation of NO and ET-1. Therefore, ACEi peptides derived from skipjack tuna (K. pelamis) muscle, especially SP and VDRYF, are beneficial components for functional food against hypertension and cardiovascular diseases.

Identification and release kinetics of peptides from tilapia skin collagen during alcalase hydrolysis

Collagen from tilapia skin was extracted and confirmed as type I collagen. Collagen was then hydrolyzed with alcalase for 4 h and the released peptides were identified. The structure-activity relationship of collagen-released peptides showed that proline at position C3 played a key role in improving ACE inhibitory activity, while proline at position C2 had a negative effect. Collagen peptide release kinetics showed that with the extension of time, the number of peptides increased dramatically at first, decreased, and then tended to be stable. This indicated that collagen peptides mainly originated from primary enzymolysis at the first stage and began to undergo secondary hydrolysis in the second stage. Afterwards, secondary enzymolysis was dominant at the third stage and finally remained stable at final two stages. Understanding the pattern of collagen peptide release kinetics might offer a powerful approach in the collagen-peptide food processing industry to better control food safety and quality.

Isolation, identification and in vivo antihypertensive effect of novel angiotensin I-converting enzyme (ACE) inhibitory peptides from Spirulina protein hydrolysate

The side effects of traditional antihypertensive drugs have driven people's interest in discovery of novel angiotensin-I converting enzyme (ACE) inhibitory peptides with efficiency and safety. Spirulina possesses abundant proteins and...

Seventeen novel angiotensin converting enzyme (ACE) inhibitory peptides from protein hydrolysate of Mytilus edulis: Isolation, identification, molecular docking study, and protective function on HUVECs

In the study, seventeen angiotensin converting enzyme (ACE) inhibitory peptides were isolated from protein hydrolysate of blue mussel (Mytilus edulis) and identified as MFR, MFV, FV, KP, QP, QVK, IK,...

Novel Angiotensin-Converting Enzyme Inhibitory Peptides Identified from Walnut Glutelin-1 Hydrolysates: Molecular Interaction, Stability, and Antihypertensive Effects

In recent years, angiotensin-converting enzyme (ACE) inhibitory peptide has become a research hotspot because of its essential role in maintaining human blood pressure balance. In this study, two novel ACE inhibitory peptides of Val-Glu-Arg-Gly-Arg-Arg-lle-Thr-Ser-Val (Valine-Glutamate-Arginine-Glycine-Arginine-Arginine-Isoleucine-Threonine-Serine-Valine, VERGRRITSV) and Phe-Val-Ile-Glu-Pro-Asn-Ile-Thr-Pro-Ala (Phenylalanine-Valine-Isoleucine-Glutamate-Proline-Asparagine-Isoleucine-Threonine-Proline-Alanine, FVIEPNITPA) were isolated and purified from defatted walnut meal hydrolysates through a series of preparation processes including ultrafiltration, Sephadex G-15 gel chromatography, and reverse high performance liquid chromatography (RP-HPLC). Both peptides showed high ACE inhibitory activities. The molecular docking study revealed that VERGRRITSV and FVIEPNITPA were primarily attributed to the formation of strong hydrogen bonds with the active pockets of ACE. The binding free energies of VERGRRITSV and FVIEPNITPA with ACE were -14.99 and -14.69 kcal/mol, respectively. Moreover, these ACE inhibitory peptides showed good stability against gastrointestinal enzymes digestion and common food processing conditions (e.g., temperature and pH, sugar, and salt treatments). Furthermore, animal experiment results indicated that the administration of VERGRRITSV or FVIEPNITPA exhibited antihypertensive effects in spontaneously hypertensive rats. Our results demonstrated that walnut could be a potential source of bioactive peptides with ACE inhibitory activity.

IAF, QGF, and QDF Peptides Exhibit Cholesterol-Lowering Activity through a Statin-like HMG-CoA Reductase Regulation Mechanism: In Silico and In Vitro Approach

In this study, in silico approaches are employed to investigate the binding mechanism of peptides derived from cowpea β-vignin and HMG-CoA reductase. With the obtained information, we designed synthetic peptides to evaluate their in vitro enzyme inhibitory activity. In vitro, the total protein extract and <3 kDa fraction, at 5000 µg, support this hypothesis (95% and 90% inhibition of HMG-CoA reductase, respectively). Ile-Ala-Phe, Gln-Gly-Phe, and Gln-Asp-Phe peptides were predicted to bind to the substrate binding site of HMGCR via HMG-CoAR. In silico, it was established that the mechanism of HMG-CoA reductase inhibition largely entailed mimicking the interactions of the decalin ring of simvastatin and via H-bonding; in vitro studies corroborated the predictions, whereby the HMG-CoA reductase activity was decreased by 69%, 77%, and 78%, respectively. Our results suggest that Ile-Ala-Phe, Gln-Gly-Phe, and Gln-Asp-Phe peptides derived from cowpea β-vignin have the potential to lower cholesterol synthesis through a statin-like regulation mechanism.

Antihypertensive activity of the ACE-renin inhibitory peptide derived from Moringa oleifera protein

Moringa oleifera (MO) leaf is a potential plant protein resource with high nutritional and medicinal value. The study aims to investigate the hypotensive activity and stability of MO leaf peptides. MO leaf protein was extracted and then hydrolyzed with Alcalase to produce the MO leaf protein hydrolysate (MOPH). The MOPH was separated into peptide fractions with different molecular weights by membrane ultrafiltration. The MOPH and ultrafiltration fractions were evaluated for antihypertensive activity. Inhibition of the angiotensin-converting enzyme (84.71 ± 0.07%) and renin (43.72 ± 0.02%) was significantly higher for <1 kDa peptides when compared to other fractions. Oral administration of the <1 kDa component in spontaneously hypertensive rats positively lowers the blood pressure (∼17 mmHg). The <1 kDa component was isolated and purified subsequently; the final active component was identified by mass spectrometry and amino acid sequence analysis. Two highly active ACE (angiotensin-converting enzyme) and renin dual inhibitory peptides Leu-Gly-Phe-Phe (LGF) and Gly-Leu-Phe-Phe (GLFF) were obtained. The two peptides exhibited a good dual inhibitory activity of ACE and renin with IC50 values of LGF (0.29 ± 0.13 mM, 1.88 ± 0.08 mM) and GLFF (0.31 ± 0.04 mM, 2.80 ± 0.08 mM). Furthermore, in vivo models, LGF and GLFF significantly reduced the systolic blood pressure (19.4 mmHg; 18.2 mmHg) and diastolic blood pressure (12 mmHg; 13.8 mmHg) of SHRs (spontaneously hypertensive rats). The peptide transmembrane transport experiments and simulated gastrointestinal digestion experiments with LGF and GLFF showed that they can resist gastrointestinal digestion in a complete form. Thus, bioactive peptides from MO leaf may possess the potential to be used for treating hypertension in humans.

Production of ACE Inhibitory Peptides from Whey Proteins Modified by High Intensity Ultrasound Using Bromelain

High Intensity Ultrasound (HIUS) can induce modification of the protein structure. The combination of enzymatic hydrolysis and ultrasound is an interesting strategy to improve the release of the Angiotensin-Converting Enzyme (ACE) inhibitory peptides. In this study, whey proteins were pretreated with HIUS at two levels of amplitude (30 and 50%) for 10 min, followed by hydrolysis using the vegetable protease bromelain. The hydrolysates obtained were ultrafiltrated and their fractions were submitted to a simulated gastrointestinal digestion. The conformational changes induced by HIUS on whey proteins were analyzed using Fourier-transform infrared spectroscopy by attenuated total reflectance (FTIR-ATR) and intrinsic spectroscopy. It was found that both levels of ultrasound pretreatment significantly decreased the IC₅₀ value (50% Inhibitory Concentration) of the hydrolysates in comparison with the control (α = 0.05). After this treatment, HIUS-treated fractions were shown as smaller in size and fractions between 1 and 3 kDa displayed the highest ACE inhibition activity. HIUS promoted significant changes in whey protein structure, inducing, unfolding, and aggregation, decreasing the content of α-helix, and increasing β-sheets structures. These findings prove that ultrasound treatment before enzymatic hydrolysis is an innovative and useful strategy that modifies the peptide profile of whey protein hydrolysates and enhances the production of ACE inhibitory peptides.

Investigation on the characteristics and mechanisms of ACE inhibitory peptides by a thorough analysis of all 8000 tripeptides via binding free energy calculation

Food-derived angiotensin I-converting enzyme (ACE) inhibitory peptides represent a potential source of new antihypertensive. However, their characteristics and binding mechanisms were not well understood. In this study, novel energy calculation and experimentation were combined to elucidate the characteristics and mechanisms of ACE inhibitory tripeptides. ACE inhibitory activity of all 8,000 tripeptides was investigated by in silico experiments. IC50 values of the five top-rated tripeptides ranged from 5.86 to 21.84 μM. Five hundred top-ranked tripeptides were chosen for detailed structure-activity analysis, and a significant preference for aromatic amino acids at both C- and N-terminus was found. By binding free energy analysis of nine representative tripeptides via MM/GBSA, electrostatic energy was found to be the leading energy that contributed to the binding of ACE with its high affinity tripeptides. Besides, S355, V380, and V518, three residues positioned around the classical binding pockets of ACE, also played a key role in ACE's binding. Therefore, for tripeptides, their binding pockets in ACE were redefined. In conclusion, the characteristics of ACE inhibitory peptides were more deeply illustrated by the thorough analysis of all tripeptides. The energy analysis allows a better understanding of the binding mechanisms of ACE inhibitory peptides, which could be used to redesign the ACE inhibitors for stronger inhibitory activity.

Purification and characterization of a novel angiotensin I-converting enzyme-inhibitory peptide derived from Alaska pollack skins

Hydrolysates containing angiotensin I-converting enzyme (ACE)-inhibitory peptide were prepared from protein of Alaska pollack skins using alcalase and trypsin. The protein hydrolysate was separated by ultrafiltration, Sephadex G-25 gel filtration chromatography and reversed phase high-performance liquid chromatography (HPLC), from which a novel purified peptide was obtained. Both random coil structure and β-sheet in the purified peptide were revealed in Fourier transform infrared spectrum. The amino sequence of the purified peptide was identified as GPLGVP, VLYPVK, VFLENVLR, and FEEF by HPLC-Q-TOF-MS (HPLC-quadrupole time-of-flight mass spectrometry). The peptide GPLGVP whose molecular weight was 538.31 Da showed the highest ACE inhibitory activity (IC₅₀  = 105.8 µM). The purified peptide featured a noncompetitive inhibition kinetic mechanism was shown in the Lineweaver-Burk plots and was susceptible to enzymes as indicated in the studies on stability of gastrointestinal proteases. Moreover, the peptide GPLGVP can combine ACE catalytic pocket through hydrogen bonds and other forces with high binding power as disclosed in molecular docking simulation, which provides the inhibitory effect of GPLGVP on ACE.

Identification, Characterization and Antihypertensive Effect In Vivo of a Novel ACE-Inhibitory Heptapeptide from Defatted Areca Nut Kernel Globulin Hydrolysates

The areca (Areca catechu L.) nut kernel (ANK) is a good potential protein source for its high protein content of 9.89-14.62 g/100 g and a high yield of around 300,000 tons per year in China. However, utilization of the areca nut kernel is limited. To expand the usage of ANK in pharmaceutical or foods industries, areca nut kernel globulin was extracted and angiotensin-I converting enzyme (ACE) inhibition peptides were prepared and identified using gel chromatography, reversed phase HPLC separation, UPLC-ESI-MS/MS analysis and in silico screening. Finally, a novel ACE-inhibitory heptapeptide (Ala-Pro-Lys-Ile-Glu-Glu-Val) was identified and chemically synthesized. The combination pattern between APKIEEV and ACE, and the inhibition kinetics, antihypertensive effect and endothlein-1 inhibition activity of APKIEEV were studied. The results of the molecular docking demonstrated that APKIEEV could bind to four active sites (not the key active sites) of ACE via short hydrogen bonds and demonstrated high ACE-inhibitory activity (IC₅₀: 550.41 μmol/L). Moreover, APKIEEV exhibited a significantly lowering effect on both the systolic blood pressure and diastolic blood pressure of spontaneously hypertensive rats, and had considerable suppression ability on intracellular endothelin-1. These results highlight the potential usage of APKIEEV as ingredients of antihypertensive drugs or functional foods.

Computational Study on Temperature Driven Structure-Function Relationship of Polysaccharide Producing Bacterial Glycosyl Transferase Enzyme

Glycosyltransferase (GTs) is a wide class of enzymes that transfer sugar moiety, playing a key role in the synthesis of bacterial exopolysaccharide (EPS) biopolymer. In recent years, increased demand for bacterial EPSs has been observed in pharmaceutical, food, and other industries. The application of the EPSs largely depends upon their thermal stability, as any industrial application is mainly reliant on slow thermal degradation. Keeping this in context, EPS producing GT enzymes from three different bacterial sources based on growth temperature (mesophile, thermophile, and hyperthermophile) are considered for in silico analysis of the structural–functional relationship. From the present study, it was observed that the structural integrity of GT increases significantly from mesophile to thermophile to hyperthermophile. In contrast, the structural plasticity runs in an opposite direction towards mesophile. This interesting temperature-dependent structural property has directed the GT–UDP-glucose interactions in a way that thermophile has finally demonstrated better binding affinity (−5.57 to −10.70) with an increased number of hydrogen bonds (355) and stabilizing amino acids (Phe, Ala, Glu, Tyr, and Ser). The results from this study may direct utilization of thermophile-origin GT as best for industrial-level bacterial polysaccharide production.

Identification of post-digestion angiotensin-I converting enzyme (ACE) inhibitory peptides from soybean protein Isolate: Their production conditions and in silico molecular docking with ACE

This study attempts to investigate natural angiotensin-I converting enzyme (ACE) inhibitors. Soybean protein isolated (SPI) hydrolysate (SPIH) was prepared by Alcalase from inexpensive SPI, and their ACE inhibitory peptides were obtained via membrane separation, ethanol precipitation and adsorption chromatography enrichment. Activated carbon was more suitable for peptide enrichment than eight macroporous resins. The peptide fraction yielded under optimal conditions (protein-active carbon mass ratio 2:1; adsorption pH 3.0 and time 2 h; desorption time 2 h) exhibited a 10.4 times higher ACE-inhibitory activity than SPIH. Novel peptides IY, YVVF, LVF, WMY, LVLL and FF (hydrophobicity values 10.51-12.87; activity scores 0.2373-0.999) might be the main contributors to SPIH's ACE inhibition. IY had the lowest IC50 (0.53 ± 0.02 μM). YVVF had the greatest affinity (-9.8 kcal/mol) for 2OC2 (ACE's C-domain receptor) via H-bonds. IY and WMY could be potent ACE inhibitors, and their ACE-inhibitory activities unaltered and increased after in vitro gastrointestinal digestion.

Design, synthesis and biological evaluation of novel pyxinol derivatives with anti-heart failure activity

Heart failure (HF) is an important and leading cause of substantial morbidity and mortality globally. The angiotensin-converting enzymatic (ACE) is the causative source for congestive heart failure. Natural products and its derivatives play a vital role in drug discovery and development owing to their efficacy and low toxicity. Pyxinol is a potent natural agent for cardiovascular disease. Thus we investigated the effect on ACE and HF of pyxinol derivatives. We designed and synthesized 32 novel fatty acid ester derivatives of pyxinol via esterification. Among them, compounds 2e (IC₅₀=105 nM) and 3b (IC₅₀=114 nM) displayed excellent ACE inhibitory activity in vitro, and exhibited non-toxic to H9c2 cells. The interactions between ACE and compounds were predicted by molecular docking respectively. In verapamil-induced zebrafish HF model, the activity assay showed that these two derivatives could improve cardiovascular physiological indexes including heart beats, venous congestion, heart dilation, cardiac output, ejection fraction and fractional shortening in a dose-dependent manner. A UPLC-QTOF-MS-based serum metabolomics approach was applied to explore the latent mechanism. A total of 25 differentiated metabolites and 8 perturbed metabolic pathways were identified. These results indicated that pyxinol fatty acid ester derivatives 2e and 3b might be considered as potent drug candidates against heart failure and deserved further research and development.

Development of delivery system based on marine chitosan: Encapsulationand release kinetic study of antioxidant peptides from chitosan microparticle

The present work aims to encapsulate goby fish protein hydrolysate (GPH), endowed with antioxidant activity, through ionic gelation process using blue crab chitosan (CH) and tripolyphosphate anions and to evaluate the structural, thermal and antioxidant properties of the elaborated microparticles (MPs). The GPH-loaded MPs present spherical shape as seen by scanning electron microscopy (SEM) images and positive zeta potential. The increase of loaded GPH concentration led to the increase of encapsulation efficiency (EE) and to the reduction of the particle size. In fact, MPs, loaded with 2 and 5 mg/ml GPH, had EE values of 44 and 58% and mean particles size of 4.81 and 3.78 μm, respectively. Furthermore, thermogravimetric analysis (TGA) profiles revealed the enhanced thermal stability of encapsulated biopeptides compared to the free ones. Release kinetic data showed a Fickian diffusion behavior which follows swelling and a diffusion-controlled mechanism for peptides liberation. Finally, as opposed to unloaded MPs, an improvement of the antioxidant activity of the loaded MPs with biopeptides was observed.

Isolation of novel ACE-inhibitory peptide from naked oat globulin hydrolysates in silico approach: Molecular docking, in vivo antihypertension and effects on renin and intracellular endothelin-1

Naked oat globulin was hydrolyzed by alcalase, flavourzyme, pepsin, and trypsin in sequence. The hydrolysates (NOGH) were purified using gel chromatography, reversed-phase high performance liquid chromatography (RP-HPLC). Finally, fraction D7d with the highest ACE-inhibitory was subjected to liquid chromatography-mass spectrometry analysis and 14 peptides were identified. Of which, peptide SSYYPFK (890.4 Da) was chose to synthesize based on in silico analysis. The SSYYPFK demonstrated high ACE-inhibitory activity (IC₅₀ : 91.82 µM) with competitive inhibition mode, and could effectively (P < 0.05) lower the systolic blood pressure and diastolic pressure of spontaneously hypertensive rats at the concentration of 100 to 150 mg/kg body weight. Molecular docking simulation demonstrated that SSYYPFK could bind with the active site S1 of ACE via short hydrogen bonds. It could remain the ACE-inhibitory activity after simulated gastrointestinal hydrolysis. Moreover, SSYYPFK showed acceptable renin and endothelin-1 suppressing capacity (47.59% and 27.88% at 1.5 mg/mL, respectively). These results indicated that SSYYPFK may have similar antihypertensive mechanism with captopril, and could be develop to natural antihypertensive products. PRACTICAL APPLICATION: One novel ACE-inhibitory peptide SSYYPFK (890.4 Da) was identified from naked oat globulin hydrolysates. It exhibited relatively high renin and intracellular endothelin-1 suppressing capacity, and could effectively (P < 0.05) lower the systolic blood pressure and diastolic pressure of spontaneously hypertensive rats. This peptide could be used as natural and safe nutraceuticals and/or functional ingredients.

Camel Hemorphins Exhibit a More Potent Angiotensin-I Converting Enzyme Inhibitory Activity than Other Mammalian Hemorphins: An In Silico and In Vitro Study

Angiotensin-I converting enzyme (ACE) is a zinc metallopeptidase that has an important role in regulating the renin-angiotensin-aldosterone system (RAAS). It is also an important drug target for the management of cardiovascular diseases. Hemorphins are endogenous peptides that are produced by proteolytic cleavage of beta hemoglobin. A number of studies have reported various therapeutic activities of hemorphins. Previous reports have shown antihypertensive action of hemorphins via the inhibition of ACE. The sequence of hemorphins is highly conserved among mammals, except in camels, which harbors a unique Q>R variation in the peptide. Here, we studied the ACE inhibitory activity of camel hemorphins (LVVYPWTRRF and YPWTRRF) and non-camel hemorphins (LVVYPWTQRF and YPWTQRF). Computational methods were used to determine the most likely binding pose and binding affinity of both camel and non-camel hemorphins within the active site of ACE. Molecular dynamics simulations showed that the peptides interacted with critical residues in the active site of ACE. Notably, camel hemorphins showed higher binding affinity and sustained interactions with all three subsites of the ACE active site. An in vitro ACE inhibition assay showed that the IC50 of camel hemorphins were significantly lower than the IC50 of non-camel hemorphins.