Analysis of novel angiotensin I-converting enzyme inhibitory peptides from enzymatic hydrolysates of cuttlefish (Sepia officinalis) muscle proteins

Antioxidant and ACE-Inhibitory Activity of Protein Hydrolysates Produced from Atlantic Sea Cucumber (Cucumaria frondosa)

Atlantic sea cucumber is a benthic marine echinoderm found in Northwest Atlantic waters and is harvested mainly for its body wall. The body wall, along with internal organs and aquaphyrangeal bulb/flower, is a rich source of proteins, where the latter parts are often considered as processing discards. The objective of this research was to produce protein hydrolysates from sea cucumber tissues (body wall, flower, and internal organs) with bioactive properties associated with antioxidants, DNA and LDL cholesterol oxidation inhibition, and angiotensin-I-converting enzyme (ACE) inhibitory effects. The protein hydrolysates were prepared using food-grade commercial enzymes, namely Alcalase, Corolase, and Flavourzyme, individually and in combination, and found that the combination of enzymes exhibited stronger antioxidant potential than the individual enzymes, as well as their untreated counterparts. Similar trends were also observed for the DNA and LDL cholesterol oxidation inhibition and ACE-inhibitory properties of sea cucumber protein hydrolysates, mainly those that were prepared from the flower. Thus, the findings of this study revealed potential applications of sea cucumber-derived protein hydrolysates in functional foods, nutraceuticals, and dietary supplements, as well as natural therapeutics.

Screening of anti-liver fibrosis peptides from turtle shell protein using two-enzyme hydrolysis by molecular docking

Turtle shell as a food residue of Pelodiscus sinensis (a type of edible aquatic animal) is widely used in Traditional Chinese Medicine for hepatic fibrosis therapy. Previous studies have demonstrated that the peptides (<6 kDa) derived from turtle shells are considered effective components. The protein of turtle shells has important potential as a source of bioactive peptides which may play a role as ingredients in functional foods. In the present study, the protein of turtle shell was hydrolyzed using a two-enzyme combination. It was found that the hydrolysates obtained by a combination of pepsin and trypsin showed the highest anti-liver fibrosis activity relative to other combinations in a cell viability assay. The hydrolysates were separated and purified by ultra-filtration (<6 kDa), gel filtration chromatography (GFC) and high-performance liquid chromatography (HPLC). Subsequently, the sequences of purified peptides were analyzed by liquid chromatography-mass spectrometry (LC-MS/MS). Molecular docking was used to analyze the interaction of these peptides with the transforming growth factor-β₁ (TGF-β₁) receptor. Two (GPPGVPGPGPL, TSLPVPAPV) of these novel peptides displayed lower binding energies to the TGF-β₁ receptor (-8.18 kcal mol^-1, -8 kcal mol^-1). Finally, the above two peptides were synthesized chemically and their in vitro anti-liver fibrosis activity was verified by MTT assay. Among them, GPPGVPGPGPL showed a better in vitro anti-liver fibrosis activity (IC50: 80.13 μM). We established a method to obtain anti-liver fibrosis peptides from turtle shells by using bioactivity-guided isolation with molecular docking. Turtle shell protein is an excellent source of anti-liver fibrosis peptides which can offer therapeutic and commercial benefits as an ingredient in functional foods.

Unconventional microbial proteases as promising tools for the production of bioactive protein hydrolysates

Enzymatic hydrolysis is the most prominent strategy to release bioactive peptides from different food proteins and protein-rich by-products. Unconventional microbial proteases (UMPs) have gaining increased attention for such purposes, particularly from the 2010s. In this review, we present and discuss aspects related to UMPs production, and their use to obtain bioactive protein hydrolysates. Antioxidant and anti-hypertensive potentials, commonly evaluated through in vitro testing, are mainly reported. The in vivo bioactivities of protein hydrolysates and peptides produced through UMPs action are highlighted. In addition to bioactivities, enzymatic hydrolysis acts by modulating the functional properties of proteins for potential food uses. The compiled literature indicates that UMPs are promising biocatalysts to generate bioactive protein hydrolysates, adding up to commercially available enzymes. From the recent interest on this topic, continuous and in-depth research is needed to advance toward the applicability and commercial utility of both UMPs and obtained hydrolysates.

A novel angiotensin I-converting enzyme inhibitory peptide derived from the trypsin hydrolysates of salmon bone proteins

When fish are processed, fish bone becomes a key component of the waste, but to date very few researchers have sought to use fish bone to prepare protein hydrolysates as a means of adding value to the final product. This study, therefore, examines the potential of salmon bone, through an analysis of the benefits of its constituent components, namely fat, moisture, protein, and ash. In particular, the study seeks to optimize the process of enzymatic hydrolysis of salmon bone with trypsin in order to produce angiotensin-I converting enzyme (ACE) inhibitory peptides making use of response surface methodology in combination with central composite design (CCD). Optimum hydrolysis conditions concerning DH (degree of hydrolysis) and ACE-inhibitory activity were initially determined using the response surface model. Having thus determined which of the salmon bone protein hydrolysates (SBPH) offered the greatest level of ACE-inhibitory activity, these SBPH were duly selected to undergo ultrafiltration for further fractionation. It was found that the greatest ACE-inhibitory activity was achieved by the SBPH fraction which had a molecular weight lower than 0.65 kDa. This fraction underwent further purification using RP-HPLC, revealing that the F7 fraction offered the best ACE-inhibitory activity. For ACE inhibition, the ideal peptide in the context of the F7 fraction comprised eight amino acids: Phe-Cys-Leu-Tyr-Glu-Leu-Ala-Arg (FCLYELAR), while analysis of the Lineweaver-Burk plot revealed that the FCLYELAR peptide can serve as an uncompetitive ACE inhibitor. An examination of the molecular docking process showed that the FCLYELAR peptide was primarily able to provide ACE-inhibitory qualities as a consequence of the hydrogen bond interactions taking place between ACE and the peptide. Furthermore, upon isolation form the SBPH, the ACE-inhibitory peptide demonstrated ACE-inhibitory capabilities in vitro, underlining its potential for applications in the food and pharmaceutical sectors.

Antioxidant and Angiotensin I-Converting Enzyme (ACE) Inhibitory Peptides Obtained from Alcalase Protein Hydrolysate Fractions of Hemp (Cannabis sativa L.) Bran

Proteins from hemp bran (HPB), a byproduct of the hemp seed food-processing chain, were chemically extracted, hydrolyzed by Alcalase, and separated by membrane ultrafiltration into four fractions (MW <1, 1-3, 3-5, and >5 kDa). The antioxidant and antihypertensive properties of the initial extract and the fractions were evaluated by in vitro assays for their ability to scavenge radical species, bind with metal ions, reduce ferric ions, and inhibit angiotensin-converting enzyme (ACE) activity. Bioactive peptides were identified by high-resolution mass spectrometry and sequence comparison with BIOPEP and BioPep DB databases. The hydrolysate was strongly antioxidant and ACE-inhibiting; the most bioactive peptides were further concentrated by ultrafiltration. Of the 239 peptides identified, 47 (12 antioxidant and 35 ACE-inhibitory) exhibited structural features correlated with the specific bioactivity. These results highlight the promise of hydrolysate and size-based HPB fractions as natural functional ingredients for the food or pharmaceutical industry.

Angiotensin I-Converting Enzyme (ACE-I) Inhibition and Antioxidant Peptide from a Squilla Species

BACKGROUND

Oratosquilla woodmasoni is one of the marine squilla species which is found in the entire Asia-Pacific region. This current study assesses the species as the main basis of both ACEi and antioxidant peptide.

OBJECTIVE

To isolate the ACEi peptide derived from O. woodmasoni and examine its ACE inhibition along with antioxidant potential.

METHODS

The squilla muscle protein was hydrolysed using alcalase and trypsin enzymes for 12 hours and tested for DH. The hydrolysates were examined for their ACEi activity, and then the best hydrolysate was sequentially purified in various chromatographical methods. The purified peptide was studied for anti-oxidant and functional properties, followed by amino acid sequencing. The purified peptide was also evaluated for its toxicity by in vitro cell viability assay.

RESULTS

The DH% was found to be 47.13 ± 0.72 % and 89.43 ± 2.06 % for alcalase and trypsin, respectively. The alcalase 5th-hour hydrolysate was detected with potent activity (65.97 ± 0.56 %) using ACEi assay and was primarily fractionated using ultrafiltration; the maximum inhibitory activity was found with 77.04 ± 0.52 % in 3-10kDa fraction. Subsequently, the fraction was purified using IEC and GFC, in which the AC1-A2 fraction had higher antihypertensive activity (70.85 ± 0.78 %). The non-toxic fraction showed hexapeptide HVGGCG with molecular weight 529 Da with a great potential of antioxidant activity along with functional property.

CONCLUSION

This peptide could be an alternative as a nutraceutical for both ACE inhibition and antioxidant.

Bioactivities and ACE-inhibitory peptides releasing potential of lactic acid bacteria in fermented soy milk

Abstract

This study was designed to evaluate the bioactivities such as β-glucosidase activity, α-galactosidase activity, and the growth behavior of the Lactobacillus cultures in soy milk medium. Ten Lactobacillus cultures were considered in this study. L. fermentum (M2) and L. casei (NK9) were selected due to their better α-galactosidase, β-glucosidase activity and growth behavior in soy milk medium during fermentation. Further, soy milk fermented with M2 showed higher proteolytic activity (0.67 OD) and ACE-inhibitory (48.44%) than NK9 (proteolytic activity: 0.48 OD and ACE-inhibitory activity: 41.33%). Bioactive peptides produced during the fermentation of soy milk using the selected Lactobacillus cultures were also identified with potent ACE-inhibitory activity by MALDI-TOF spectrometry, and the identified ACE inhibitory peptide sequences from fermented soy milk were characterized using Biopep database.

Graphical abstract

Antioxidant properties and inhibition of angiotensin-converting enzyme by highly active peptides from wheat gluten

This study aimed to focus on the high-value utilization of raw wheat gluten by determining the potent antioxidant peptides and angiotensin I-converting enzyme (ACE) inhibitory peptides from wheat gluten oligopeptides (WOP). WOP were analyzed for in vitro antioxidant activity and inhibition of ACE, and the identification of active peptides was performed by reversed-phase high-performance liquid chromatography and mass spectrometry. Quantitative analysis was performed for highly active peptides. Five potent antioxidant peptides, Leu-Tyr, Pro-Tyr, Tyr-Gln, Ala-Pro-Ser-Tyr and Arg-Gly-Gly-Tyr (6.07 ± 0.38, 7.28 ± 0.29, 11.18 ± 1.02, 5.93 ± 0.20 and 9.04 ± 0.47 mmol 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) equivalent/g sample, respectively), and five potent ACE inhibitory peptides, Leu-Tyr, Leu-Val-Ser, Tyr-Gln, Ala-Pro-Ser-Tyr and Arg-Gly-Gly-Tyr (half maximal inhibitory concentration (IC50) values = 0.31 ± 0.02, 0.60 ± 0.03, 2.00 ± 0.13, 1.47 ± 0.08 and 1.48 ± 0.11 mmol/L, respectively), were observed. The contents of Leu-Tyr, Pro-Tyr, Tyr-Gln, Ala-Pro-Ser-Tyr, Arg-Gly-Gly-Tyr, and Leu-Val-Ser were 155.04 ± 8.36, 2.08 ± 0.12, 1.95 ± 0.06, 22.70 ± 1.35, 0.25 ± 0.01, and 53.01 ± 2.73 μg/g, respectively, in the WOP. Pro-Tyr, Tyr-Gln, Ala-Pro-Ser-Tyr, Arg-Gly-Gly-Tyr, and Leu-Val-Ser are novel antioxidative/ACE inhibitory peptides that have not been previously reported. The results suggest that WOP could potentially be applied in the food industry as a functional additive.

Influence of conventional and recent extraction technologies on physicochemical properties of bioactive macromolecules from natural sources: A review

The incorporation of bioactive macromolecules from natural sources into marketable functional foods and nutraceuticals is of major significance to the agri-food sector. Interest in this area of research stems from the application of purified bioactive macromolecules in enhancing food quality and as an alternative to some pharmaceutical drugs for delivery of potential health benefits, with less associated adverse effects. To obtain bioactive macromolecules of high quality, appropriate use of extraction techniques and its influence on sensory and physicochemical properties is paramount. With the advent of technology-aided processes, there has been remarkable improvement in the extraction efficiency of these bioactive agents. An overview of the influence of these new techniques on extraction efficiency and physicochemical properties of proteins, lipids and fibers, which this detailed review provides, will prove to be a valuable resource to food industries aiming to maximize production of bioactive macromolecules from natural sources as well as the scientific community.

Effects of natural peptides from food proteins on angiotensin converting enzyme activity and hypertension

Cardiovascular diseases are the leading cause of death. The underlying pathophysiology is largely contributed by an overactivation of the renin-angiotensin-aldosterone-system (RAAS). Herein, angiotensin II (AngII) is a key mediator not only in blood pressure control and vascular tone regulation, but also involved in inflammation, endothelial dysfunction, atherosclerosis, hypertension and congestive heart failure. Since more than three decades suppression of AngII generation by inhibition of the angiotensin-converting enzyme (ACE) or blockade of the AngII-receptor has shown clinical benefit by reducing hypertension, atherosclerosis and other inflammation-associated cardiovascular diseases. Besides pharmaceutical ACE-inhibitors some natural peptides derived from food proteins reduce in vitro ACE activity. Several animal studies and a few human clinical trials have shown antihypertensive effects of such peptides, which might be attractive as food additives to prevent age-related RAAS activation. However, their inhibitory potency on in vitro ACE activity does not always correlate with an antihypertensive impact. While some peptides with high inhibitory activity on ACE-activity in vitro show no antihypertensive effect in vivo, other peptides with only a moderate ACE inhibitory activity in vitro cause such effects. The explanation for this conflicting phenomenon between inhibitory activity and antihypertensive effect remains unclear to date. This review shall critically address the effects of natural peptides derived from different food proteins on the cardiovascular system and the possible underlying mechanisms. A central aspect will be to point to conceptual gaps in the current understanding of the action of these peptides with respect to in vivo blood pressure lowering effects.

STRUCTURAL CHARACTERISTICS AND ANTIHYPERTENSIVE EFFECTS OF ANGIOTENSIN-I-CONVERTING ENZYME INHIBITORY PEPTIDES IN THE RENIN-ANGIOTENSIN AND KALLIKREIN KININ SYSTEMS

BACKGROUND

The commercially available synthetic angiotensin-I-converting enzyme (ACE) inhibitors are known to exert negative side effects which have driven many research groups globally to discover the novel ACE inhibitors.

METHOD

Literature search was performed within the PubMed, ScienceDirect.com and Google Scholar.

RESULTS

The presence of proline at the C-terminal tripeptide of ACE inhibitor can competitively inhibit the ACE activity. The effects of other amino acids are less studied leading to difficulties in predicting potent peptide sequences. The broad specificity of the enzyme may be due to the dual active sites observed on the somatic ACE. The inhibitors may not necessarily competitively inhibit the enzyme which explains why some reported inhibitors do not have the common ACE inhibitor characteristics. Finally, the in vivo assay has to be carried out before the peptides as the antihypertensive agents can be claimed. The peptides must be absorbed into circulation without being degraded, which will affect their bioavailability and potency. Thus, peptides with strong in vitro IC50 values do not necessarily have the same effect in vivo and vice versa.

CONCLUSION

The relationship between peptide amino acid sequence and inhibitory activity, in vivo studies of the active peptides and bioavailability must be studied before the peptides as antihypertensive agents can be claimed.

Protein Hydrolysates and Biopeptides: Production, Biological Activities, and Applications in Foods and Health Benefits. A Review

In recent years, a great deal of interest has been expressed regarding the production, characterization, and applications of protein hydrolysates and food-derived biopeptides due to their numerous beneficial health effects. In this regard, research is mainly focused on investigating the therapeutic potential of these natural compounds. Based on their amino acids composition, sequences, hydrophobicity, and length, peptides released from food proteins, beyond their nutritional properties, can exhibit various biological activities including antihypertensive, antioxidative, antithrombotic, hypoglycemic, hypocholesterolemic, and antibacterial activities among others. Protein hydrolysates are essentially produced by enzymatic hydrolysis of whole protein sources by appropriate proteolytic enzymes under controlled conditions, followed by posthydrolysis processing to isolate desired and potent bioactive peptides from a complex mixture of active and inactive peptides. Therefore, because of their human health potential and safety profiles, protein hydrolysates and biopeptides may be used as ingredients in functional foods and pharmaceuticals to improve human health and prevent diseases. In this review, we have focused on the major variables influencing the enzymatic process of protein hydrolysates production. The biological properties of protein hydrolysates will be described as well as their applications in foods and health benefits.

A Review of Potential Marine-derived Hypotensive and Anti-obesity Peptides

Bioactive peptides are food derived components, usually consisting of 3-20 amino acids, which are inactive when incorporated within their parent protein. Once liberated by enzymatic or chemical hydrolysis, during food processing and gastrointestinal transit, they can potentially provide an array of health benefits to the human body. Owing to an unprecedented increase in the worldwide incidence of obesity and hypertension, medical researchers are focusing on the hypotensive and anti-obesity properties of nutritionally derived bioactive peptides. The role of the renin-angiotensin system has long been established in the aetiology of metabolic diseases and hypertension. Targeting the renin-angiotensin system by inhibiting the activity of angiotensin-converting enzyme (ACE) and preventing the formation of angiotensin II can be a potential therapeutic approach to the treatment of hypertension and obesity. Fish-derived proteins and peptides can potentially be excellent sources of bioactive components, mainly as a source of ACE inhibitors. However, increased use of marine sources, poses an unsustainable burden on particular fish stocks, so, the underutilized fish species and by-products can be exploited for this purpose. This paper provides an overview of the techniques involved in the production, isolation, purification, and characterization of bioactive peptides from marine sources, as well as the evaluation of the ACE inhibitory (ACE-I) activity and bioavailability.

Two angiotensin-converting enzyme-inhibitory peptides from almond protein and the protective action on vascular endothelial function

This study aimed to discover and prepare novel angiotensin converting enzyme (ACE) inhibitory peptides from almond protein and further evaluate the effect on endothelial function of human umbilical vascular endothelial cells (HUVECs). Almond protein was hydrolyzed using a two-stage alcalase-protamex hydrolysis process, and the hydrolysates were subjected to a series of separations, ultrafiltration, gel filtration chromatography, and reversed-phased preparative chromatography, to obtain the active peptides. Seven ACE inhibitory fractions with the molecular weight below 1.5 kDa were isolated and prepared, and two purified ACE inhibitory peptides with the IC50 values of 67.52 ± 0.05 and 43.18 ± 0.07 μg mL(-1), were identified as Met-His-Thr-Asp-Asp and Gln-His-Thr-Asp-Asp, respectively. Then the effect of two ACE inhibitory peptides on the endothelial function of HUVECs was evaluated. Results showed that the two potent ACE inhibitory peptides significantly regulated the release of nitric oxide and endothelin in HUVECs. These results suggest that almond peptides have potential as an antihypertensive nutraceuticals or a functional food ingredient.

Production of the angiotensin I converting enzyme inhibitory peptides and isolation of four novel peptides from jellyfish (Rhopilema esculentum) protein hydrolysate

BACKGROUND

Angiotensin I converting enzyme (ACE) plays an important role in regulating blood pressure in the human body. ACE inhibitory peptides derived from food proteins could exert antihypertensive effects without side effects. Jellyfish (Rhopilema esculentum) is an important fishery resource suitable for production of ACE inhibitory peptides. The objective of this study was to optimize the hydrolysis conditions for production of protein hydrolysate from R. esculentum (RPH) with ACE inhibitory activity, and to isolate and identify the ACE inhibitory peptides from RPH.

RESULTS

Rhopilema esculentum protein was hydrolyzed with Compound proteinase AQ to produce protein hydrolysate with ACE inhibitory activity, and the hydrolysis conditions were optimized using response surface methodology. The optimum parameters for producing peptides with the highest ACE inhibitory activity were as follows: hydrolysis time 3.90 h, hydrolysis temperature 58 °C, enzyme:substrate ratio 2.8% and pH 7.60. Under these conditions, the ACE inhibitory rate reached 32.21%. In addition, four novel ACE inhibitory peptides were isolated, and their amino acids sequences were identified as Val-Gly-Pro-Tyr, Phe-Thr-Tyr-Val-Pro-Gly, Phe-Thr-Tyr-Val-Pro-Gly-Ala and Phe-Gln-Ala-Val-Trp-Ala-Gly, respectively. The IC50 value of the purified peptides for ACE inhibitory activity was 8.40, 23.42, 21.15 and 19.11 µmol L(-1) .

CONCLUSION

These results indicate that the protein hydrolysate prepared from R. esculentum might be a commercial competitive source of ACE inhibitory ingredients to be used in functional foods. © 2015 Society of Chemical Industry.

Two novel peptides with angiotensin I converting enzyme inhibitory and antioxidative activities from Scorpaena notata muscle protein hydrolysate

Fish protein hydrolysate was prepared from muscle of small red scorpionfish (Scorpaena notata) by treatment with a protease from the fungus Penicillium digitatum. Protein hydrolysate was found to strongly inhibit the angiotensin I converting enzyme and exhibited high antioxidative activity through 1,1-diphenyl-2-picrylhydrazyl free radical scavenging assay. After ultrafiltration, peptides were isolated by a two-step procedure: size exclusion chromatography on a Toyopearl HW-40 followed by reversed-phase high-performance liquid chromatography with a high purification yield of 2.5 mg of peptide per gram of initial protein. Two major peptides were then identified by nanoscale liquid chromatography coupled to tandem mass spectrometry (nano-LC-MS/MS), corresponding to the following sequences: Leu-Val-Thr-Gly-Asp-Asp-Lys-Thr-Asn-Leu-Lys (1,204.665 Da) and Asp-Thr-Gly-Ser-Asp-Lys-Lys-Gln-Leu (992.511 Da). These peptides, mainly composed of hydrophilic amino acids, showed high antioxidative and angiotensin I converting enzyme inhibitory activities. These data suggest that the two novel peptides isolated from the muscle hydrolysate of small red scorpionfish can be a beneficial ingredient for functional foods or pharmaceuticals against hypertension and oxidative stress.

Identification of Angiotensin I-Converting Enzyme Inhibitory Peptides Derived from Enzymatic Hydrolysates of Razor Clam Sinonovacula constricta

Angiotensin I-converting enzyme (ACE) inhibitory activity of razor clam hydrolysates produced using five proteases, namely, pepsin, trypsin, alcalase, flavourzyme and proteases from Actinomucor elegans T3 was investigated. Flavourzyme hydrolysate showed the highest level of degree of hydrolysis (DH) (45.87%) followed by A. elegans T3 proteases hydrolysate (37.84%) and alcalase (30.55%). The A. elegans T3 proteases was observed to be more effective in generating small peptides with ACE-inhibitory activity. The 3 kDa membrane permeate of A. elegans T3 proteases hydrolysate showed the highest ACE-inhibitory activity with an IC50 of 0.79 mg/mL. After chromatographic separation by Sephadex G-15 gel filtration and reverse phase-high performance liquid chromatography, the potent fraction was subjected to MALDI/TOF-TOF MS/MS for identification. A novel ACE-inhibitory peptide (VQY) was identified exhibiting an IC50 of 9.8 μM. The inhibitory kinetics investigation by Lineweaver-Burk plots demonstrated that the peptide acts as a competitive ACE inhibitor. The razor clam hydrolysate obtained by A. elegans T3 proteases could serve as a source of functional peptides with ACE-inhibitory activity for physiological benefits.

Peptides derived from Rhopilema esculentum hydrolysate exhibit angiotensin converting enzyme (ACE) inhibitory and antioxidant abilities

Jellyfish (Rhopilema esculentum) was hydrolyzed using alcalase, and two peptides with angiotensin-I-converting enzyme (ACE) inhibitory and antioxidant activities were purified by ultrafiltration and consecutive chromatographic methods. The amino acid sequences of the two peptides were identified as VKP (342 Da) and VKCFR (651 Da) by electrospray ionization tandem mass spectrometry. The IC₅₀ values of ACE inhibitory activities of the two peptides were 1.3 μM and 34.5 μM, respectively. Molecular docking results suggested that VKP and VKCFR bind to ACE through coordinating with the active site Zn(II) atom. Free radical scavenging activity and protection against hydrogen peroxide (H₂O₂)-induced rat cerebral microvascular endothelial cell (RCMEC) injury were used to evaluate the antioxidant activities of the two peptides. As the results clearly showed that the peptides increased the superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-px) activities in RCMEC cells), it is proposed that the R. esculentum peptides exert significant antioxidant effects.

Characterization of ACE inhibitory peptides from Mactra veneriformis hydrolysate by nano-liquid chromatography electrospray ionization mass spectrometry (Nano-LC-ESI-MS) and molecular docking

Food-derived bioactive compounds are gaining increasing significance in life sciences. In the present study, we identified angiotensin I-converting enzyme (ACE)-inhibitory peptides from Mactra veneriformis hydrolysate using a nano-LC-MS/MS method. Mactra veneriformis hydrolysate was first separated into four fractions (F1–F4) based on molecular weight by ultrafiltration. The fraction with molecular weight lower than 1 kDa (F1) showed the highest ACE inhibitory activity. F1 was then analyzed by a high throughput nano-LC-MS/MS method and sequences of peptides in F1 were calculated accordingly. The 27 peptides identified as above were chemically synthesized and tested for ACE-inhibitory activity. The hexapeptide VVCVPW showed the highest potency with an IC₅₀ value of 4.07 μM. We then investigated the interaction mechanism between the six most potent peptides and ACE by molecular docking. Our docking results suggested that the ACE inhibitory peptides bind to ACE via interactions with His383, His387, and Glu411 residues. Particularly, similar to the thiol group of captopril, the cysteine thiol group of the most potent peptide VVCVPW may play a key role in the binding of this peptide to the ACE active site.

Identification of the major ACE-inhibitory peptides produced by enzymatic hydrolysis of a protein concentrate from cuttlefish wastewater

The aim of this work was the purification and identification of the major angiotensin converting enzyme (ACE) inhibitory peptides produced by enzymatic hydrolysis of a protein concentrate recovered from a cuttlefish industrial manufacturing effluent. This process consisted on the ultrafiltration of cuttlefish softening wastewater, with a 10 kDa cut-off membrane, followed by the hydrolysis with alcalase of the retained fraction. Alcalase produced ACE inhibitors reaching the highest activity (IC₅₀ = 76.8 ± 15.2 μg mL⁻¹) after 8 h of proteolysis. Sequential ultrafiltration of the 8 h hydrolysate with molecular weight cut-off (MWCO) membranes of 10 and 1 kDa resulted in the increased activity of each permeate, with a final IC₅₀ value of 58.4 ± 4.6 μg mL⁻¹. Permeate containing peptides lower than 1 kDa was separated by reversed-phase high performance liquid chromatography (RP-HPLC). Four fractions (A–D) with potent ACE inhibitory activity were isolated and their main peptides identified using high performance liquid chromatography coupled to an electrospray ion trap Fourier transform ion cyclotron resonance-mass spectrometer (HPLC-ESI-IT-FTICR) followed by comparison with databases and de novo sequencing. The amino acid sequences of the identified peptides contained at least one hydrophobic and/or a proline together with positively charged residues in at least one of the three C-terminal positions. The IC₅₀ values of the fractions ranged from 1.92 to 8.83 μg mL⁻¹, however this study fails to identify which of these peptides are ultimately responsible for the potent antihypertensive activity of these fractions.

Pharmacological evidence of bradykinin regeneration from extended sequences that behave as peptidase-activated B2 receptor agonists

While bradykinin (BK) is known to be degraded by angiotensin converting enzyme (ACE), we have recently discovered that Met-Lys-BK-Ser-Ser is paradoxically activated by ACE. We designed and evaluated additional "prodrug" peptides extended around the BK sequence as potential ligands that could be locally activated by vascular or blood plasma peptidases. BK regeneration was estimated using the contractility of the human umbilical vein as model of vascular functions mediated by endogenous B2 receptors (B2Rs) and the endocytosis of the fusion protein B2R-green fluorescent protein (B2R-GFP) expressed in Human Embryonic Kidney 293 cells. Of three BK sequences extended by a C-terminal dipeptide, BK-His-Leu had the most desirable profile, exhibiting little direct affinity for the receptor but a significant one for ACE (as shown by competition of [(3)H]BK binding to B2R-GFP or of [(3)H]enalaprilat to recombinant ACE, respectively). The potency of the contractile effect of this analog on the vein was reduced 18-fold by the ACE inhibitor enalaprilat, pharmacologically evidencing BK regeneration in situ. BK-Arg, a potential substrate of arginine carboxypeptidases, had a low affinity for B2Rs and its potency as a contractile agent was reduced 15-fold by tissue treatment with an inhibitor of these enzymes, Plummer's inhibitor. B2R-GFP internalization in response to 100 nM of the extended peptides recapitulated these findings, as enalaprilat selectively inhibited the effect of BK-His-Leu and Plummer's inhibitor, that of BK-Arg. The two peptidase inhibitors did not affect BK-induced effects in either assay. The novel C-terminally extended BKs had no or very little affinity for the kinin B1 receptor (competition of [(3)H]Lys-des-Arg(9)-BK binding). The feasibility of peptidase-activated B2R agonists is illustrated by C-terminal extensions of the BK sequence.

Novel angiotensin I-converting enzyme inhibitory peptides from enzymatic hydrolysates of goby (Zosterisessor ophiocephalus) muscle proteins

In recent years, food protein-derived bioactive peptides have received considerable attention because of their numerous health benefits. Amongst bioactive peptides, those with antihypertensive activity are receiving special attention due to their role in cardiovascular diseases. Goby protein hydrolysates (GPHs) prepared by treatment with five different crude bacterial proteases were found to exhibit varying degrees of angiotensin I-converting enzyme (ACE) inhibitory activity. The hydrolysate generated by the crude protease from Bacillus mojavensis A21, which displayed the highest ACE inhibitory activity, was further fractionated by size exclusion chromatography on a Sephadex G-25 and reversed-phase high performance liquid chromatography (RP-HPLC). The molecular masses and amino acid sequences of five peptides, in sub-fraction F5-2, which exhibited the highest ACE inhibitory activity, were determined using ESI-MS and ESI-MS/MS, respectively. The structures of these peptides were identified as Ala-Arg-Ser, Val-Val-Ala-Pro-Phe-Ala-His-Gly-Thr, Arg-Ser-Thr-Ala, Phe-Tyr-Pro-Pro, Arg-Cys-Ser-Ala-Gly-Val. Further, the sequences of fifteen peptides in the F5-4 sub-fraction, which exhibited high activity, were determined. Therefore, GPHs have a potential as hypotensive nutraceutical ingredients.

BIOLOGICAL SIGNIFICANCE

Peptides find many outlets of application in the biotechnological field, amongst which are pharmaceutical applications. Progression amongst new small molecules deposited like substance medicamentous blows itself. In this context, large pharmaceutical companies invest in peptide research to open therapeutic new prospects. Even if they are used as therapeutic agents for nearly one century in their natural form, the use of peptides remains parsimonious although we experienced a significant development since a few tens of years, in particular thanks to the clarification of the methods of production, chemical in solid or biological phase such as in phage display. Peptides present many advantages compared to traditional drugs that have small molecules, Generation of bioactive peptides by proteolysis of food proteins, using exogenous proteases, is a new and interesting approach for the production and identification of new and potent specific hypotensive agents. From another side, compared with natural peptides isolated from different sources, there is more diversity in structure and mode of action of the derived bioactive peptides. In fact, proteolysis of protein substrates, having different amino acid composition and sequences, by proteases having different specificities may generate numerous specific peptide inhibitors, with different lengths and amino acid sequences. These bioactive peptides have received considerable attention for their effectiveness in both the prevention and the treatment of hypertension.

Angiotensin I-Converting Enzyme Inhibitory Peptides of Chia (Salvia hispanica) Produced by Enzymatic Hydrolysis

Synthetic angiotensin I-converting enzyme (ACE-I) inhibitors can have undesirable side effects, while natural inhibitors have no side effects and are potential nutraceuticals. A protein-rich fraction from chia (Salvia hispanica L.) seed was hydrolyzed with an Alcalase-Flavourzyme sequential system and the hydrolysate ultrafiltered through four molecular weight cut-off membranes (1 kDa, 3 kDa, 5 kDa, and 10 kDa). ACE-I inhibitory activity was quantified in the hydrolysate and ultrafiltered fractions. The hydrolysate was extensive (DH = 51.64%) and had 58.46% ACE-inhibitory activity. Inhibition ranged from 53.84% to 69.31% in the five ultrafiltered fractions and was highest in the <1 kDa fraction (69.31%). This fraction's amino acid composition was identified and then it was purified by gel filtration chromatography and ACE-I inhibition measured in the purified fractions. Amino acid composition suggested that hydrophobic residues contributed substantially to chia peptide ACE-I inhibitory strength, probably by blocking angiotensin II production. Inhibitory activity ranged from 48.41% to 62.58% in the purified fractions, but fraction F1 (1.5–2.5 kDa) exhibited the highest inhibition (IC₅₀ = 3.97 μg/mL; 427–455 mL elution volume). The results point out the possibility of obtaining bioactive peptides from chia proteins by means of a controlled protein hydrolysis using Alcalase-Flavourzyme sequentional system.

Nine novel angiotensin I-converting enzyme (ACE) inhibitory peptides from cuttlefish (Sepia officinalis) muscle protein hydrolysates and antihypertensive effect of the potent active peptide in spontaneously hypertensive rats

This study aimed to identify novel ACE inhibitory peptides from the muscle of cuttlefish. Proteins were hydrolyzed and the hydrolysates were then subjected to various types of chromatography to isolate the active peptides. Nine ACE inhibitory peptides were isolated and their molecular masses and amino acid sequences were determined using ESI-MS and ESI-MS/MS, respectively. The structures of the most potent peptides were identified as Val-Glu-Leu-Tyr-Pro, Ala-Phe-Val-Gly-Tyr-Val-Leu-Pro and Glu-Lys-Ser-Tyr-Glu-Leu-Pro. The first peptide displayed the highest ACE inhibitory activity with an IC50 of 5.22μM. Lineweaver-Burk plots suggest that Val-Glu-Leu-Tyr-Pro acts as a non-competitive inhibitor against ACE. Furthermore, antihypertensive effects in spontaneously hypertensive rats (SHR) also revealed that oral administration of Val-Glu-Leu-Tyr-Pro can decrease systolic blood pressure significantly (p<0.01). These results suggest that the Val-Glu-Leu-Tyr-Pro would be a beneficial ingredient for nutraceuticals and pharmaceuticals acting against hypertension and its related diseases.

Enzyme Hydrolysates from Stichopus horrens as a New Source for Angiotensin-Converting Enzyme Inhibitory Peptides

Stichopus horrens flesh was explored as a potential source for generating peptides with angiotensin-converting enzyme (ACE) inhibitory capacity using 6 proteases, namely alcalase, flavourzyme, trypsin, papain, bromelain, and protamex. Degree of hydrolysis (DH) and peptide profiling (SDS-PAGE) of Stichopus horrens hydrolysates (SHHs) was also assessed. Alcalase hydrolysate showed the highest DH value (39.8%) followed by flavourzyme hydrolysate (32.7%). Overall, alcalase hydrolysate exhibited the highest ACE inhibitory activity (IC₅₀ value of 0.41 mg/mL) followed by flavourzyme hydrolysate (IC₅₀ value of 2.24 mg/mL), trypsin hydrolysate (IC₅₀ value of 2.28 mg/mL), papain hydrolysate (IC₅₀ value of 2.48 mg/mL), bromelain hydrolysate (IC₅₀ value of 4.21 mg/mL), and protamex hydrolysate (IC₅₀ value of 6.38 mg/mL). The SDS-PAGE results showed that alcalase hydrolysate represented a unique pattern compared to others, which yielded potent ACE inhibitory peptides with molecular weight distribution lower than 20 kDa. The evaluation of the relationship between DH and IC₅₀ values of alcalase and flavourzyme hydrolysates revealed that the trend between those parameters was related to the type of the protease used. We concluded that the tested SHHs would be used as a potential source of functional ACE inhibitory peptides for physiological benefits.