Highest Angiotensin I-converting Enzyme Research Articles

Identification of a Novel Post-digestion Angiotensin I-Converting Enzyme Inhibitory Peptide from Silver Prussian Carp (Carassius auratus gibelio) Roe

Proteins of aquatic products are potential sources of bioactive peptides. This study attempted to screen 29 kinds of aquatic products with the highest angiotensin I-converting enzyme (ACE) inhibitory activity and to identify the active peptide. Results showed that the enzyme hydrolysate of silver Prussian carp roe exhibited the highest ACE inhibitory rate before (64.71%) and after (53.82%) digestion. LAKVAP identified from the enzymatic extract of silver Prussian carp roe was a competitive inhibitor, with an ACE inhibitory rate of 95.33%. The molecular docking study suggested that LAKVAP formed hydrogen bonds with S2 active sites (Gln281, His 353, and His513) and made coordinate bonds with Zn2+ (His383) of ACE, which contributed to the interaction between ACE and peptide. The results suggested that silver Prussian carp roe proteins could be suitable materials for ACE inhibitory peptide preparation, and LP-6 might be potentially beneficial as an antihypertensive agent.

Effects of dual-frequency slit ultrasound on the enzymolysis of high-concentration hydrolyzed feather meal: Biological activities and structural characteristics of hydrolysates

Ultrasound-assisted enzymolysis has been applied to improve conventional enzymolysis, while there are rare reports on the application of ultrasound to high-concentration feather protein enzymolysis. Therefore, the feasibility of dual-frequency slit ultrasound (DFSU) for enzymolysis of high-concentration hydrolyzed feather meal (HFM), as well as the biological activities and structural characteristics of hydrolysates were investigated. The single-factor test was used to optimize the ultrasonic processing parameters: substrate concentration, frequency mode, intermittent ratio, power density, and time. The results showed that protein recovery rate and conversion rate increased by 6.08% and 18.63% under the optimal conditions (200 g/L, 28/80 kHz, 5:2 s/s, 600 W/L, and 3 h) compared with conventional enzymolysis, respectively. The macromolecular proteins in hydrolysates were converted into micromolecular peptides (< 500 Da) when treated by DFSU, and antioxidant activity and angiotensin-I-converting enzyme (ACE) inhibitory activity of hydrolysates were increased. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images illustrated the microstructure changes of feather protein particles in the ultrasound-assisted enzymatic hydrolysates of HFM (UEH), including more porous, smaller, and more uniform. Additionally, the conformation of protein molecules was significantly affected (P < 0.05), including the increase in free sulfhydryl (SH), the decrease in disulfide bond (SS) and surface hydrophobicity (H0). Fourier transform infrared (FTIR) spectra analysis further showed that the secondary structure of feather proteins was modified with a reduction in α-helix, β-turn, and β-sheet, while an increase in random coil content was observed. These results indicated that DFSU could be a promising method to enhance high-concentration HFM for preparing peptide-rich hydrolysates with high antioxidant activity and ACE inhibitory activity.

Effects of Inherent Lactic Acid Bacteria on Inhibition of Angiotensin I-Converting Enzyme and Antioxidant Activities in Dry-Cured Meat Products.

The aim of this study was to investigate the inherent bacteria that contribute to expressing the angiotensin I-converting enzyme (ACE) inhibitory activity and the antioxidant activity of dry-cured meat products without a bacterial starter. Among the ten dry-cured meat product samples, Coppa and Milano salami exhibited high ACE inhibitory activity, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability, and oxygen radical absorbance capacity (ORAC). No consistent trend was observed in the pH values or the total peptide and imidazole dipeptide concentration of the products that exhibited high ACE inhibitory and antioxidant activities in the tested samples. To investigate the bacteria contributing to the ACE inhibitory and antioxidant activities of the product, 16S rRNA sequencing analysis, isolation, and identification of bacteria were performed using not only Coppa and Milano salami but also the Jamon Serrano and Parma prosciutto products that had low functional activities. Results suggest the Lactobacillales order, particularly the species Latilactobacillus sakei and Pediococcus pentosaceus, were the main inherent bacteria in Coppa and Milano salami, respectively, compared with the Jamon Serrano and Parma prosciutto products. Therefore, the inherent lactic acid bacteria in dry-cured meat products without bacterial starter is important for ACE inhibitory and antioxidant activities of the products.

In vitro gastrointestinal digestion study and identification of novel angiotensin i-converting enzyme inhibitory peptide from broccoli (brassica oleracea)

Due to the side effects of synthetic ACE inhibitors like captopril used for the treatment of hypertension, ACE inhibitory peptides derived from natural sources have attracted increasing attention in recent years. The aim of this work was to screen the vegetable with the highest angiotensin I-converting enzyme (ACE) inhibitory activity from 50 kinds of vegetables by using three different extraction methods, and to purify and identify the novel peptides from broccoli protein hydrolysates and evaluated the ACE inhibitory activity in vitro. Through centrifugation, ultrafltration, gel chromatography and high performance liquid chromatography (HPLC), the fraction BHs-IV-I-IV of the enzyme hydrolysate of broccoli with 100% ACE inhibitory activity was obtained. The novel ACE inhibitory peptide (KSVLLKF, KF-7) was identifed from fraction BHs-IV-I-IV by ultra-performance liquid chromatographytandem mass spectrometry (UPLC-MS/MS). ACE inhibition rate of 0.05 mg of KF-7 reached 42.86%, whereas 12.48 mg of pepsin hydrolysate of broccoli crude extract only exhibited 55.29% of ACE inhibition rate, indicating the low content of KF-7 in the protein hydrolysates of broccoli. These results suggested that KF-7 has a potential application in functional foods/pharmaceutical agents against hypertension and protein from broccoli may constitute a potential antihypertensive peptide source.

Effect of mono- and dual frequency power ultrasound assisted enzymolysis on the degree of hydrolysis and ACE inhibitory activity of Stevia protein hydrolysates

&#x0D; &#x0D; &#x0D; &#x0D; Purpose: To study the effects of ultrasound pretreatment at different frequencies and working modes, including mono frequency ultrasound (MFU) and dual-frequency ultrasound (DFU), on the degree of hydrolysis (DH) and angiotensin-I-converting enzyme (ACE) inhibitory effect of Stevia protein (SP).&#x0D; Methods: Protein from Stevia leaves was extracted by water (50 g suspended in 1000 mL). The hydrolysis of stevia protein extract (SPE) was carried out using alcalase at 5 % enzyme substrate (E/S) ratio. A study was then carried out to investigate its microstructure and morphology using scanning electron microscopy (SEM).&#x0D; Results: The results showed that ultrasound pretreatment did not increase DH of SP significantly (p &gt; 0.05). However, the highest ACE inhibitory activity of stevia protein hydrolysate was obtained at DFU level (20/50 KHz). Overall, ultrasonic frequency mode had a significant influence on ACE inhibitory activity.&#x0D; Conclusion: The frequency selection of ultrasound pretreatment of SP is essential for the preparation of ACE inhibitory peptide.&#x0D; &#x0D; &#x0D; &#x0D;

Enrichment of γ-aminobutyric acid in mulberry leaves and the inhibitory effects of the water extract on ACE and α-glucosidase activity

To improve the functional properties of mulberry leaves, different methods were used to treat harvested mulberry leaves to accumulate γ-aminobutyric acid (GABA). The results showed that soaking, cold shock, and anoxic treatments all significantly increased GABA content in mulberry leaves, which were all closely related to the increase of glutamate decarboxylase (GAD) activity and Ca2+ content. Further studies showed that the water extract of the treated mulberry leaves had a higher angiotensin I-converting enzyme (ACE) inhibitory activity than that of the untreated sample, which was close to the effects of using the same amount of GABA alone. The result of molecular docking showed that GABA was stretched into the hydrophobic pocket of ACE to form a stable hydrophobic binding with Ala-354 and Val-380 residues, and formed the hydrogen bond interaction with the residue Glu-384. Importantly, GABA could directly chelated with the zinc ion (bond lengths: 2.9 and 3.1 Å), which was the main interaction between the GABA and ACE. However, the inhibition of mulberry leaf extract on α-glucosidase was not closely related to the GABA content. The results showed that the α-glucosidase inhibitory activity was significantly increased by treating with 6 g/L sodium glutamate for 15 h (IC50 =0.29 mg/mL), and further LC/MS analysis demonstrated that some active compounds especially neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid and rutin were significantly increased in the extract. These data indicated that GABA enrichment was an effective postharvest treatment of mulberry leaves, which can improve its prospects as functional raw materials for industrial production.

A pivotal peptide (Ile-Leu-Lys-Pro) with high ACE- inhibitory activity from duck egg white: identification and molecular docking

Salted duck egg white was desalted and hydrolyzed to produce angiotensin I-converting enzyme (ACE) inhibitory peptides. Single factor test and response surface design were performed to determine the best hydrolysis conditions: enzyme dosage 11875.99 U/g, substrate concentration 33.04 g/L and hydrolysis time 4 h. The fraction V (MW < 1 kDa), which exhibited the strongest ACE inhibitory activity, was characterized by HPLC-ESI-MS/MS. Eighty-three peptides were identified, and among them Ile-Leu-Lys-Pro, Ile-Asn-Ser-Trp, Ile-Arg and His-Pro-Ala were synthesized for further research. Ile-Leu-Lys-Pro exhibited the highest ACE inhibitory activity (IC50: 0.355 mM). The molecular docking studies revealed that nine amino acids contributed to stabilize the docking complex. The ACE inhibition of Ile-Leu-Lys-Pro and Ile-Asn-Ser-Trp were mainly attributed to Ile in N-terminal. The residues Glu362 and Ala332 were the important binding sites in molecular docking. This research expands the understanding of ACE inhibitory peptides from duck egg white as well as highlights an opportunity for recycling an otherwise discarded byproduct.

Algae as a source of peptides inhibitors of the angiotensin-converting enzyme: a systematic review.

Hypertension is a factor that contributes to the risk of chronic diseases. The inhibition of angiotensin-I converting enzyme (ACE) is a useful therapeutic approach to the hypertension treatment. The algae have been an alternative for the production of ACE inhibitory (ACEi) peptides from enzymatic hydrolysis due to their protein-rich biomass. The aim of this study was to systematically review the literature regarding the production, composition and activity of ACEi peptides derived from algae proteins. Systematic database searches identified 648 related articles. Among these, only 14 were selected according to the eligibility criteria to this review. Macroalgae are more studied than microalgae as sources of ACEi peptides. Furthermore, hydrolysates by thermolysin or bromelain exhibited the highest ACEi activity compared to other enzymes. The main features of the peptides with high ACE inhibition are low molecular weight, short amino acids sequence and non-competitive inhibition pattern. In vivo studies using hydrolysates and peptides derived from algae proteins showed antihypertensive activity in spontaneously hypertensive rats (SHR). Thus, it is suggested that ACEi peptides derived from algae can be considered as potential antihypertensive.

Effect of legume varieties and fermentation time of tempe using usar inoculum on the inhibitory activity of angiotensin I-converting enzyme

Abstract. Indrati R, Handayani MT, Rahayu NA, Pebrianti SA. 2021. Effect of legume varieties and fermentation time of tempe using usar inoculum on the inhibitory activity of angiotensin I-converting enzyme. Biodiversitas 22: 5262-5267. The effect of three varieties of legumes, namely, velvet bean (Mucuna prurient), lima bean (Phasaelus lunatus L.), and pigeon pea (Cajanus cajan), on the activity of angiotensin I-converting enzyme (ACE) inhibitors was studied during tempe fermentation. Fermentation is one way to produce bioactive peptides. Furthermore, the effect of inoculum usar on tempe fermentation was studied. Hydrophobic amino acids are essential in binding firmly to the active site of ACE, and the research showed that pigeon pea had higher levels of hydrophobic amino acids compared with soybeans. The legumes affected the protease activity, peptide content, degree of hydrolysis, and production of ACE inhibitory (ACEI) activity during tempe fermentation. High protein levels and peptide content did not guarantee a high ACE inhibitor level. The mixed culture of usar caused no effect on the production of ACE inhibitors compared with a single culture of Raprima. Legume beans that reached optimal fermentation fast produced high levels of ACE inhibitors. Of the three types of legumes tested in the study, lima beans had the highest ACEI activity during fermentation.

Enzymatic Hydrolysis Optimization for Preparation of Tuna Dark Meat Hydrolysate with Antioxidant and Angiotensin I-Converting Enzyme (ACE) Inhibitory Activities

ABSTRACT The hydrolysates of tuna dark meat with high angiotensin I-converting enzyme (ACE) inhibitory and antioxidant activities were prepared using three enzymes. The effect of concentration (0.5–3.0%, w/w) and hydrolysis time (30–180 min) on yield, degree of hydrolysis (DH), ACE inhibitory activities, and antioxidant capacity was determined. The optimum conditions were the same: 180 min extraction while the concentration of alcalase, neutrase, and flavourzyme were 2.43, 2.62, and 2.62% (w/w), respectively. The hydrolysate resulted in the range of 36.5–50.0% for DH, 5.79–7.71% for yield, 0.29–1.11, 0.28–0.53, and 0.24–0.31 mg/mL IC50 values with 2,2-diphenyi-l-picrylhydrazyl radical (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), and ACE inhibitory activity, respectively, and 0.41–1.35 FeSO4/g for ferric reducing antioxidant power (FRAP). The hydrolysates showed high solubility. Emulsion stability and emulsifying activity index decreased, while foam stability and expansion increased with increasing concentration. Hydrolysates using flavourzyme were fractioned using ultrafiltration membranes. The <1 kDa fraction had significantly higher ACE inhibitory and antioxidant activities.

Angiotensin I converting enzyme (ACE) inhibitory peptides derived from alfalfa ( Medicago sativa L.) leaf protein and its membrane fractions

Alfalfa leaf proteins (ALP) were extracted through the method of alkali solubilization and acid precipitation, and the six different ALP hydrolysates were obtained by hydrolysis of papain, Alcalase, Neutrase, trypsin, pepsin, and Flavourzyme, respectively. The results showed that alfalfa leaf protein hydrolysate (ALPH) prepared by papain exhibited the highest angiotensin I converting enzyme (ACE) inhibitory activity of 79.69% ± 2.77% at the same concentration. Hence, papain ultimately was used to hydrolyze ALP for producing ACE inhibitory activity peptides. The hydrolysis conditions of hydrolysis temperature, enzyme to substrate ratio (E/S), and pH were optimized by using response surface methodology (RSM). We obtained the maximum ACE inhibitory rate of 92.33% ± 0.30% under E/S of 3%, pH of 7.5 and hydrolysis temperature of 55 ºC. Finally, the hydrolysate was separated into four ranges of molecular weight (ALPH-1, >30 kDa; ALPH-2, 30–10 kDa; ALPH-3, 10–5 kDa; ALPH-4, <5 kDa) through different ultrafiltration membranes. Among them, ALPH-4 showed the maximum ACE inhibitory activity of 93.85% ± 1.09%, implying that ALPH-4 should be considered as a potential source of natural ACE inhibitor. Novelty impact statement Recently, more and more researches focus on ACE inhibitors which are derived from food because they are safer than the synthetic chemicals which may result in several adverse events. We found that ACE inhibitory peptides from Alfalfa leaf protein have the high ACE inhibitory activity in vitro, which could be considered as a potential approach for use in nutraceuticals for the prevention and management of hypertension. People have a high demand to consume functional products, this has driven the food industry to the development of a new commercial ACE inhibitory peptides products in the market.

Amaranth proteins as potential source of bioactive peptides with enhanced inhibition of enzymatic markers linked with hypertension and diabetes

The health and environmental concerns are provoking changes in human diets and plant-based proteins are being considered as sustainable source of proteins compared to animal-derived proteins. In line with this, the current study investigated amaranth protein isolate (API) and hydrolysates (APHs) for in-vitro angiotensin-I converting enzyme (ACE), dipeptidyl peptidase-IV (DPP-IV), and α-glucosidase (AG) inhibitory activities. Amaranth protein hydrolysates (APHs) were generated by bromelain, chymotrypsin, and pronase E for 2, 4, and 6 h. All APHs, especially bromelain-4 h hydrolysate (B4) displayed enhanced ACE, DPP-IV, and AG inhibition compared to API and other APHs. About 116 peptides were identified in B4 by LC-MS-QToF and 17 peptides were predicted to be bioactive. Six of these peptides were predicted to possess high ACE inhibiting potential, while peptides FPFPPTLGY and FPFPR were found to bind to the highest number of active hotspots of DPP-IV and AG, respectively. Overall, this study demonstrated that APHs could be a potential source of antidiabetic and antihypertensive peptides for functional food formulation.

Characterization of ACE Inhibitory Peptides Prepared from Pyropia pseudolinearis Protein

More than 7000 red algae species have been classified. Although most of them are underused, they are a protein-rich marine resource. The hydrolysates of red algal proteins are good candidates for the inhibition of the angiotensin-I-converting enzyme (ACE). The ACE is one of the key factors for cardiovascular disease, and the inhibition of ACE activity is related to the prevention of high blood pressure. To better understand the relationship between the hydrolysates of red algal proteins and the inhibition of ACE activity, we attempted to identify novel ACE inhibitory peptides from Pyropia pseudolinearis. We prepared water soluble proteins (WSP) containing phycoerythrin, phycocyanin, allophycocyanin, and ribulose 1,5-bisphosphate carboxylase/oxygenase. In vitro analysis showed that the thermolysin hydrolysate of the WSP had high ACE inhibitory activity compared to that of WSP. We then identified 42 peptides in the hydrolysate by high-performance liquid chromatography and mass spectrometry. Among 42 peptides, 23 peptides were found in chloroplast proteins. We then synthesized the uncharacterized peptides ARY, YLR, and LRM and measured the ACE inhibitory activity. LRM showed a low IC50 value (0.15 μmol) compared to ARY and YLR (1.3 and 5.8 μmol). In silico analysis revealed that the LRM sequence was conserved in cpcA from Bangiales and Florideophyceae, indicating that the novel ACE inhibitory peptide LRM was highly conserved in red algae.

Functional Properties of Nori Seaweed (Pyropia yezoensis) with Different Quality and Ulva sp.

ABSTRACT Nori (Pyropia yezoensis) is a widely eaten red seaweed, and its quality is decreased by the environment in which it is grown, resulting in discolored nori. Ulva sp. is green seaweed that grows in large quantities due to eutrophication. The functions of the two seaweeds were investigated for effective utilization. The total phenolic contents of discolored nori with poor quality and Ulva sp. were 56.6% and 13.0% of that in normal nori, respectively. For superoxide dismutase (SOD)-like activity, the IC50 value of normal nori was 4.33 ± 2.18 mg/mL, while that of discolored nori was 7.1-fold higher. For the coloring components, discolored nori showed a much smaller carotenoid absorbance at 400–500 nm. The amounts of hydrolysate obtained from discolored nori and Ulva sp. using protease were 74% and 30% of that of normal nori, respectively. Regarding angiotensin I-converting enzyme (ACE) inhibitory activity of the hydrolysate, normal and discolored nori seaweed had similar activities. Green seaweed Ulva sp. had a higher ACE inhibitory activity than that of nori (IC50 values: 0.045 mg/mL for Ulva sp. and 0.170 mg/mL for nori). Nori and Ulva sp. extracts had small inhibitory activities for α-glucosidase and sucrase, which manages the sugar level in blood.

Heterotrophic Microalgae Cultivation Using Jellyfish Protein Extract to Produce Bioactive Peptides

Jellyfish are often seen as a nuisance, and while attempts have been made to use jellyfish waste as fertilizer and food, they have not proved fruitful. In this study, proteins extracted from jellyfish (Aurelia aurita) are investigated as a novel nutrient source in culture medium and tested on aerial microalgae under heterotrophic condition. Results demonstrated that Vischeria helvetica KGU-Y001 heterotrophically grew in the extract-containing culture medium in the presence of light. Decomposition of the extracted protein in the culture medium containing V. helvetica cells was verified both in the presence and absence of light. The inhibitory activity of angiotensin I-converting enzyme (ACE) was measured in the culture medium when in the presence of light. The hydrolysates in the medium were separated using a gel filtration column and a peptide fraction with approximately 400 Da, and high ACE inhibitory activity (IC50 = 72 µg mL−1) was obtained. The results presented here will help to facilitate the development of culture systems with jellyfish waste as a resource for culture medium.

In vitro antioxidant and angiotensin I-converting enzyme inhibitory properties of peptides derived from corn gluten meal

Corn gluten meal (CGM) was hydrolyzed by Alcalase 2.4L and Protex 7L to obtain low-molecular-weight peptides. The antioxidant and angiotensin-I-converting enzyme (ACE) inhibitory activities of the peptides were determined by 2,2′-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) free radical scavenging activity, the JHH7 cell oxidative stress model, and the ACE inhibition assay, respectively. Corn peptides (CPs) had strong antioxidant capacity to scavenge ABTS radicals (1.44 ± 0.11 mmol/g), and significantly reduced reactive oxygen species and malondialdehyde levels in oxidized JHH7 cells, increasing superoxide dismutase, catalase, and glutathione peroxidase activities by 26.20%, 147.52%, and 43.20%, respectively, at the concentration of 800 μg/mL. CPs had high ACE inhibitory activity, with an IC50 value of 0.27 ± 0.05 mg/mL. Next, the CPs were separated by reverse-phase high-performance liquid chromatography. Twelve fractions were collected, and their ABTS free radical scavenging and ACE inhibitory activities were determined. Fractions 1, 2, 3, 4, and 9 showed higher ABTS free radical scavenging and ACE inhibitory activities. Twelve peptides were identified from active fractions by liquid chromatography–tandem mass spectrometry (LC–MS/MS) as Leu-Ser-Pro-Tyr, Leu-Asn-Ser-Pro-Ala-Tyr, Tyr-Gly-Pro-Gln, Pro-Pro-Tyr, Ala-Tyr-Pro-Glu, Thr-Tyr-Ser-Gly-Pro-Lys, Ala-Tyr-Pro-Gly-Pro-Gln, Leu-Ala-Tyr-Pro-Gln, Ala-Tyr-Leu-Gln-Gln-Gln, Ser-Ala-Pro, Asn-Ala-Pro, and Val-Asn-Ala-Pro. These peptides exhibited good ABTS free radical scavenging and ACE inhibitory activities. Therefore, CPs may have potential applications in the food industry as functional material additives.

Hydrolysis of whey protein as a useful approach to obtain bioactive peptides and a β-Lg fraction with different biotechnological applications

Most of the studies related to the susceptibility of the main bovine whey proteins to the action of cardosins of Cynara cardunculus have underestimated the potential of these proteases to hydrolyse β-Lactoglobulin (β-Lg). These works used the one-factor-at-a-time methodology, which ignores the interactions and can lead to misleading conclusions. In this work, the hydrolysis of bovine whey protein, exploiting the joint action of cardosins A and B of C. cardunculus, was optimised. For that purpose, a second-order rotatable design (with two variables at five levels) was used to study the combined effect of pH and temperature on the degree of hydrolysis (DH), the number of peptides generated and the angiotensin I-converting enzyme (ACE)-inhibitory activity.The complete hydrolysis of α-Lactalbumin (α-La) was achieved at pH 6.99/35.86 °C and pH 5.01/64.14 °C, and contrary to the previous studies, cardosins were able to hydrolyse β-Lg (up to ~40%) at pH 6.29/50 °C. In addition, the statistical analysis revealed that the same pH and temperature values that led to a minimum DH for α-La also provide a maximum DH for β-Lg.At pH 5.3 and 60 °C, we have obtained abundant peptides with high angiotensin I-converting enzyme (ACE)-inhibitory activity, but also a non-hydrolysed β-Lg. So, the purification and identification of the bioactive peptides, produced under these hydrolysis conditions, was performed. Moreover, the biotechnological potential of the β-Lg obtained was successfully proved for 3 promising applications: heat-induced gels, nanofibrils (self-assembly) and microparticles (spray-dryer).

Anti-Hypertensive Activity of Novel Peptides Identified from Olive Flounder (Paralichthys olivaceus) Surimi.

There is a growing interest in the health benefits of functional foods. A benefit that has been long sought is the control of hypertension through dietary approaches. Hypertension has been implicated as a risk factor for cardiovascular disease and is therefore of clinical significance. Here, we aim to demonstrate the antihypertensive activity of novel peptides derived from surimi, a functional food ingredient made from refined fish myofibrillar proteins. Three peptides, Ile-Val-Asp-Arg (IVDR), Trp-Tyr-Lys (WYK), and Val-Ala-Ser-Val-Ile (VASVI), were isolated from surimi made from the olive flounder (Paralichthys olivaceus). Our results show that IVDR, WYK, and VASVI exhibited high Angiotensin I-converting Enzyme (ACE) inhibition activity. These peptides are also shown to increase phosphorylation of protein kinase B (Akt) and endothelial nitric oxide synthase (eNOS), and significantly promote nitric oxide (NO) production in human umbilical vein endothelial cells. Oral administration of the peptides decreased blood pressure in spontaneously hypertensive rats (SHRs), thereby confirming that the peptides derived from surimi perform antihypertensive activity via the Akt/eNOS pathway. These results indicate that surimi made from P. olivaceus contains novel antihypertensive peptides that could be used to enhance the health benefits of food ingredients.

Angiotensin-I converting enzyme inhibitory peptide derived from the shiitake mushroom (Lentinula edodes).

Angiotensin-I converting enzyme (ACE) inhibitors are widely used to control hypertension. In this study, protein hydrolysates from shiitake mushroom were hydrolyzed to prepare ACE-inhibitory peptides. Optimum process conditions for the hydrolysis of shiitake mushrooms using Alcalase were optimized using response surface methodology. Monitoring was conducted to check the degree of hydrolysis (DH) and ACE inhibitory activity. In the results, the optimum condition with the highest DH value of 28.88% was 50.2°C, 3-h hydrolysis time, and 1.16 enzyme/substrate ratios. The highest ACE inhibitory activity (IC50 of 0.33μg/mL) was under 47°C, 3h 28min hydrolysis time, and 0.59 enzyme/substrate ratios. The highest activity was fractionated into 5 ranges of molecular weight, and the fraction below 0.65kDa showed the highest activity with IC50 of 0.23μg/mL. This fraction underwent purification using RP-HPLC, meanwhile the peak which offered a retention time of about 37min showed high ACE inhibitory activity. Mass spectrometry identified the amino acid sequence of this peak as Lys-Ile-Gly-Ser-Arg-Ser-Arg-Phe-Asp-Val-Thr (KIGSRSRFDVT), with a molecular weight of 1265.43Da. The synthesized variant of this peptide produced an ACE inhibitory activity (IC50) of 37.14μM. The peptide KIGSRSRFDVT was shown to serve as a non-competitive inhibitor according to the Lineweaver-Burk plot findings. A molecular docking study was performed, which showed that the peptide binding occurred at an ACE non-active site. The findings suggest that peptides derived from shiitake mushrooms could serve either as useful components in pharmaceutical products, or in functional foods for the purpose of treating hypertension.

Identification of novel angiotensin I‐converting enzyme inhibitory peptide from collagen hydrolysates and its molecular inhibitory mechanism

SummaryThe fish collagen protein was hydrolysed and further fractionated into four molecular weight ranges by ultrafiltration. Subsequently, the peptide fraction with the potent angiotensin I‐converting enzyme (ACE) inhibitory activity was identified. The potential inhibitory mechanism of the peptide was clarified by molecular docking. As a result, FCPH‐Ⅳ with molecular weight between 600 and 1000 Da exerted the high ACE inhibitory activity and was identified by de novo peptide sequencing. The peptide GHVGAAGS exhibited significant ACE inhibitory activity with the IC50 value of 407.28 ± 3.55 μm. In addition, the docking results showed the interactions between the amino acids at the four positions closest to the C‐terminal site of GHVGAAGS and the major active residues (GLN281, HIS353, LYS511 and HIS513) of ACE lead to the conformational change in ACE. This work indicates that fish collagen could be utilised to produce ACE inhibitory peptides and develop health products.