QIGLF, a novel angiotensin I-converting enzyme-inhibitory peptide from egg white protein

Preparation, design, identification and application of self-assembly peptides from seafood: A review

Hydrogels formed by self-assembling peptides with low toxicity and high biocompatibility have been widely used in food and biomedical fields. Seafood contains rich protein resources and is also one of the important sources of natural bioactive peptides. The self-assembled peptides in seafood have good functional activity and are very beneficial to human health. In this review, the sequence of seafood self-assembly peptide was introduced, and the preparation, screening, identification and characterization. The rule of self-assembled peptides was elucidated from amino acid sequence composition, amino acid properties (hydrophilic, hydrophobic and electric), secondary structure, interaction and peptide properties (hydrophilic and hydrophobic). It was introduced that the application of hydrogels formed by self-assembled peptides, which lays a theoretical foundation for the development of seafood self-assembled peptides in functional foods and the application of biological materials.

Identification of novel α-glucosidase and ACE inhibitory peptides from Douchi using peptidomics approach and molecular docking

In this study, the effect of Douchi extract (DWE) on α-glucosidase and angiotensin-converting enzymes (ACE) were investigated, and several novel peptides with inhibitory activity against α-glucosidase and ACE were identified using peptidomics approach based on UPLC-MS/MS. The average inhibition rates of DWE on α-glucosidase and ACE were 73.75-78.10% and 4.56-27.07%, respectively. In the DWE, a total of 710 peptides were detected. Two novel peptides with potential inhibitory activity against α-glucosidase were identified using the correlation analysis, database alignment and molecular docking methods. They were DVFRAIPSEVL and DRPSINGLAGAN, with the IC50 values of 0.121 and 0.128 mg/mL, respectively. Also, four novel peptides with potential inhibitory activity against ACE were identified: PSSPFTDLWD, EEQDERQFPF, PVPVPVQQAFPF and PSSPFTDL, with IC50 values of 1.388, 0.041, 0.761 and 0.097 mg/mL, respectively. These results indicated that combining peptidomics and molecular docking is an effective alternative strategy for rapidly screening numbers of novel bioactive peptides from foods.

Current Trends and Applications of Food-derived Antihypertensive Peptides for the Management of Cardiovascular Disease

Abstract:

Food derived Antihypertensive peptides is considered as a natural supplement for controlling the hypertension. Food protein not only serve as a macronutrient but also act as raw material for biosynthesis of physiologically active peptides. Food sources like milk and milk products, animal protein such as meat, chicken, fish, eggs and plant derived proteins from soy, rice, wheat, mushroom, pumpkins contain high amount of antihypertensive peptides. The food derived antihypertensive peptides has ability to supress the action of rennin and Angiotesin converting enzyme (ACE) which is mainly involved in regulation of blood pressure by RAS. The biosynthesis of endothelial nitric oxide synthase is also improved by ACE inhibitory peptides which increase the production of nitric oxide in vascular walls and encourage vasodilation. Interaction between the angiotensin II and its receptor is also inhibited by the peptides which help to reduce hypertension. This review will explore the novel sources and applications of food derived peptides for the management of hypertension.

Activity and bioavailability of food protein-derived angiotensin-I-converting enzyme-inhibitory peptides

Angiotensin-I-converting enzyme (ACE) inhibitory peptides are able to inhibit the activity of ACE, which is the key enzymatic factor mediating systemic hypertension. ACE-inhibitory peptides can be obtained from edible proteins and have the function of antihypertension. The amino acid sequences and the secondary structures of ACE-inhibitory peptides determine the inhibitory activities and stability. The resistance of ACE-inhibitory peptides to digestive enzymes and peptidase affect their antihypertensive bioactivity in vivo. In this paper, the mechanism of ACE-inhibition, sources of the inhibitory peptides, structure-activity relationships, stability during digestion, absorption and transportation of ACE-inhibitory peptides, and consumption of ACE-inhibitory peptides are reviewed, which provide guidance to the development of new functional foods and production of antihypertensive nutraceuticals and pharmaceuticals.

Bioactive Peptides and Hydrolysates from Egg Proteins as a New Tool for Protection Against Cardiovascular Problems

The aim of the present work is to review the potential beneficial effects of dietary supplementation with bioactive egg protein hydrolysates or peptides on cardiometabolic changes associated with oxidative stress. The development of nutritionally improved food products designed to address specific health concerns is of particular interest because many bioactive food compounds can be potentially useful in various physiological functions such as for reducing oxidative stress. The results presented suggest that egg hydrolysates or derived peptides could be included in the diet to prevent and/or reduce some cardiometabolic complications associated with oxidative stress-related diseases.

Use of Alcalase in the production of bioactive peptides: A review

This review aims to cover the uses of the commercially available protease Alcalase in the production of biologically active peptides since 2010. Immobilization of Alcalase has also been reviewed, as immobilization of the enzyme may improve the final reaction design enabling the use of more drastic conditions and the reuse of the biocatalyst. That way, this review presents the production, via Alcalase hydrolysis of different proteins, of peptides with antioxidant, angiotensin I-converting enzyme inhibitory, metal binding, antidiabetic, anti-inflammatory and antimicrobial activities (among other bioactivities) and peptides that improve the functional, sensory and nutritional properties of foods. Alcalase has proved to be among the most efficient proteases for this goal, using different protein sources, being especially interesting the use of the protein residues from food industry as feedstock, as this also solves nature pollution problems. Very interestingly, the bioactivities of the protein hydrolysates further improved when Alcalase is used in a combined way with other proteases both in a sequential way or in a simultaneous hydrolysis (something that could be related to the concept of combi-enzymes), as the combination of proteases with different selectivities and specificities enable the production of a larger amount of peptides and of a smaller size.

Construction and Application of Membrane-Bound Angiotensin-I Converting Enzyme System: A New Approach for the Evaluation of Angiotensin-I Converting Enzyme Inhibitory Peptides

The effect of the plasma membrane on the activity of angiotensin-I converting enzyme (ACE) plays a crucial role in the evaluation of food-derived ACE inhibitory peptides, although these peptides are commonly evaluated in the system with ACE in its free state. In this study, we constructed an in vitro membrane-bound ACE C domain system to simulate the presence of the plasma membrane. The resultant K_m and V_max suggested that the presence of the membrane reduced the affinity between ACE C domain and hippuryl-histidyl-leucine, while it increased the reaction velocity. The ACE inhibitory activity of four egg white peptides and five structurally modified peptides suggested that a moderate hydrophobicity/hydrophilicity of the peptide is beneficial for the improvement of their ACE inhibitory activity in a membrane-bound system. These results also indicated that the N terminal plays a significant role in the ACE inhibitory activity of peptides in the membrane-bound system.

Novel ACE inhibitory tripeptides from ovotransferrin using bioinformatics and peptidomics approaches

Food-derived ACE inhibitory peptides have recently attracted increased attention. This work focused on a more efficient in silico method to find ACE inhibitory peptides from ovotransferrin. In this work, ovotransferrin was digested into peptides by virtual enzymolysis. Subsequently, in vitro ACE inhibitory activity of potential tripeptides was conducted following the peptide score, toxicity, and water solubility prediction. Both pharmacophore study and flexible docking were applied to analyze ACE inhibition mechanism of tripeptides. Our results demonstrated that EWL was a potent ACE inhibitory tripeptide with IC₅₀ value of 380 ± 10 μM. Besides, pharmacophore and flexible docking showed that the pi interaction and hydrogen bond were the key interactions in ACE-EWL complex. It appears that the in vitro ACE inhibitory activity of tripeptide EWL was consistent with its molecular modeling.

Identification and Characterization of Gastrointestinal-Resistant Angiotensin-Converting Enzyme Inhibitory Peptides from Egg White Proteins

Egg proteins are recognized as excellent sources of bioactive peptides, such as angiotensin-converting enzyme inhibitory (ACEi) peptides. Oral administration of a thermolysin-digested egg white hydrolysate (T-EWH) caused a significant blood pressure reduction in spontaneously hypertensive rats; a further ACEi assay implied that its ACEi activity was enhanced after in vitro gastrointestinal (GI) digestion. These results indicated that T-EWH contained ACEi peptides resisting GI digestion and/or being further released during GI digestion. Therefore, the objective of this study was to identify these responsible ACEi peptides from T-EWH. The conventionally activity-guided fractionation was applied, coupled with a synchronized GI digestion throughout, during which both peptide yield and ACEi activity before and after the GI digestion were measured. Finally, six ACEi peptides (LAPYK, LKISQ, LKYAT, INKVVR, LFLIKH, and LGHWVY) with good GI resistance were identified with IC₅₀ values <20 μM, especially LKYAT (0.09 μM). The structure-activity relationship of these peptides was discussed. The discovery of GI-resistant ACEi peptides could further support the application of egg white proteins as functional food ingredients.

Recently isolated antidiabetic hydrolysates and peptides from multiple food sources: a review

Diabetes, a metabolic syndrome of global importance has been on a progressive rise in recent years. Several pharmacological approaches have been made, which have proved effective, but with underlying side effects. Bioactive hydrolysates (BHs) and peptides (BPs) from food sources, however, have shown the relative advantage of imparting less adverse effects. Furthermore, BHs and BPs from food have been discovered to impart their antidiabetic potentials through one or more mechanisms such as inhibition of digestive enzymes, inhibition of the antigenic enzyme - Dipeptyl peptidase IV (DPP-IV), decrease in blood glucose levels and increase in insulin uptake. Several plants and animal sources have been used as protein sources for the isolation of antidiabetic hydrolysates and peptides through different mechanisms and analytical techniques. This review integrates recent research information about several popular and unconventional food sources of BHs and BPs, their isolation techniques, antidiabetic effects and protein profiles. In addition, the fractionation technique(s) employed in each study and inhibition potentials of BHs and BPs are reviewed. This article is intended to supplement accessible scholarly literature and intellectual awareness on the subject of food-oriented approach for the management of diabetes.

Identification and molecular docking study of novel angiotensin-converting enzyme inhibitory peptides from Salmo salar using in silico methods

BACKGROUND

In order to circumvent some challenges of the classical approach, the in silico method has been applied to the discovery of angiotensin-converting enzyme (ACE) inhibitory peptides from food proteins. In this study, some convenient and efficient in silico tools were utilized to identify novel ACE inhibitory peptides from Salmo salar.

RESULTS

Collagen from Salmo salar was digested in silico into hundreds of peptides. Results revealed that tetrapeptides PGAR and IGPR showed potent ACE inhibitory activity, with IC₅₀ values of 0.598 ± 0.12 and 0.43 ± 0.09 mmol L^-1 , respectively. The molecular docking result showed that PGAR and IGPR interact with ACE mostly via hydrogen bonds and attractive charge. Peptide IGPR interacts with Zn⁺ at the ACE active site, showing high inhibitory activity.

CONCLUSION

Interaction with Zn⁺ in ACE may lead to higher inhibitory activity of peptides, and Pi interactions may promote the effect of peptides on ACE. The in silico method can be an effective method to predict potent ACE inhibitory peptides from food proteins. © 2018 Society of Chemical Industry.

Egg Protein-Derived Bioactive Peptides: Preparation, Efficacy, and Absorption

The hen's egg is an important protein source of human diet. On average one large egg contains ~6g protein, which contributes to ~11% of daily protein intake. As a high-quality protein, egg proteins are well recognized as excellent sources of bioactive peptides. The objectives of this chapter are to introduce generation, bioactivities, and absorption of egg protein-derived bioactive peptides. Research on egg protein-derived bioactive peptides has been progressed during the past decades. Enzymatic hydrolysis is the major technique to prepare bioactive peptides from egg protein. Quantitative structure-activity relationships-aided in silico prediction is increasingly applied as a promising tool for efficient prediction of novel bioactive peptides. A number of bioactive peptides from egg proteins have been characterized for antioxidant, immunomodulatory, antihypertensive, antidiabetic, anticancer, and antimicrobial activities. Egg protein-derived peptides that can improve bone health have been reported as well. However, molecular mechanisms of many peptides are not fully understood. The stability and absorption routes, bioavailability, safety, and production of bioactive peptides await further investigation.

A novel fluorescent peptidyl probe for highly sensitive and selective ratiometric detection of Cd(ii) in aqueous and bio-samplesviametal ion-mediated self-assembly

A fluorescent peptidyl probe based on a Cd(ii)-triggered self-assembling process was proposed for ratiometric detection for Cd(ii) in urine and live cells.

Bioactive peptides derived from egg proteins: A review

Egg proteins have various functional and biological activities which make them potential precursor proteins for bioactive peptide production. Simulated in vitro gastrointestinal digestion and enzymatic hydrolysis using non-gastrointestinal proteases have been used as tools to produce these peptides. Bioactive peptides derived from egg proteins are reported to display various biological activities, including angiotensin I-converting enzyme (ACE) inhibitory (antihypertensive), antioxidant, antimicrobial, anti-inflammatory, antidiabetic and iron-/calcium-binding activities. More importantly, simulated in vitro gastrointestinal digestion has indicated that consumption of egg proteins has physiological benefits due to the release of such multifunctional peptides. This review encompasses studies reported to date on the bioactive peptide production from egg proteins.

In vitro antioxidant activities of the novel pentapeptides Ser-His-Glu-Cys-Asn and Leu-Pro-Phe-Ala-Met and the relationship between activity and peptide secondary structure

BACKGROUND

Using high-performance liquid chromatography/tandem mass spectrometry, two novel antioxidant pentapeptides [Ser-His-Glu-Cys-Asn (SHECN) and Leu-Pro-Phe-Ala-Met (LPFAM)] were identified from 1-3-kDa soybean protein hydrolysates (SPH). The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay was used to evaluate cytotoxicity in HepG2 cells. Antioxidant activity was measured using in vitro assays, including the cellular antioxidant activity assay (CAA), 2,2-diphenyl-1-picrylhydrazyl or 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) inhibition, and oxygen radical absorbance capacity (ORAC) assays. Finally, the secondary structure was determined using circular dichroism (CD).

RESULTS

The results revealed that two novel peptides were nontoxic and possessed antioxidant activity. SHECN had significantly higher antioxidant activity than LPFAM (P < 0.05). The CAA value of SHECN was 776.22 µmol QE 100 g^-1 . SHECN also showed significant DPPH inhibition (70.18 ± 4.06%) and ABTS inhibition (88.16 ± 0.76%). It had normalized ORAC values of 0.3000 ± 0.0070 µmol GE mg^-1 and 0.0900 ± 0.0020 µmol TE mg^-1 , respectively. The results of the CD analysis demonstrated that, compared to LPFAM, which had much lower antioxidant activity, SHECN had a high β-sheet content and reduced α-helix content.

CONCLUSION

The results indicated that SHECN possessed high antioxidant activity. A higher β-sheet content and lower content levels of α-helix appear to be correlated with antioxidant activity. © 2016 Society of Chemical Industry.

Recent Research in Antihypertensive Activity of Food Protein-derived Hydrolyzates and Peptides

Year to year obesity prevalence, reduced physical activities, bad habits/or stressful lifestyle, and other environmental and physiological impacts lead to increase in diseases such as coronary heart disease, stroke, cancer, diabetes, and hypertension worldwide. Hypertension is considered as one of the most common serious chronic diseases; however, discovery of medications with high efficacy and without side effects for treatment of patients remains a challenge for scientists. Recent trends in functional foods have evidenced that food bioactive proteins play a major role in the concepts of illness and curing; therefore, nutritionists, biomedical scientists, and food scientists are working together to develop improved systems for the discovery of peptides with increased potency and therapeutic benefits. This review presents a recent research carried out to date for the purpose of isolation and identification of bioactive hydrolyzates and peptides with angiotensin I converting enzyme inhibitory activity and antihypertensive effect from animal, marine, microbial, and plant food proteins. Effects of food processing and hydrolyzation conditions as well as some other impacts on formation, activity, and stability of these hydrolyzates and peptides are also presented.

Direct inhibition of Keap1–Nrf2 interaction by egg-derived peptides DKK and DDW revealed by molecular docking and fluorescence polarization

DKK and DDW, egg-derived direct inhibitors of the Keap1–Nrf2 interaction, screening by fluorescence polarization assays and cell experiments.

Short- and long-term antihypertensive effect of egg protein-derived peptide QIGLF

BACKGROUND

The present study aimed to investigate the in vivo antihypertensive effect on spontaneously hypertensive rats (SHRs) induced by egg protein-derived peptide QIGLF, which has been previously characterized in vitro as a potent angiotensin-converting enzyme inhibitor.

RESULTS

In vivo antihypertensive effect of QIGLF orally administered was evaluated by the tail-cuff method. The systolic blood pressure and the diastolic blood pressure of rats were measured 0, 5, 10, 15 and 20 h after administration every day. Subsequently, the effect of QIGLF on angiotensin-converting enzyme mRNA expression in the kidney of SHRs was evaluated by a polymerase chain reaction. Systolic blood pressure was found to be reduced markedly in the SHRs after a single oral administration.

CONCLUSION

The results show that the effect of QIGLF (50 mg kg^-1 body weight) was similar to that of captopril (10 mg kg^-1 body weight) with respect to lowering systolic blood pressure in SHRs. Therefore, egg white protein-derived peptide QIGLF may be useful in the prevention or treatment of hypertension. © 2016 Society of Chemical Industry.

Egg-derived bioactive peptides with ACE-inhibitory properties: a literature update

Egg proteins contain a wide set of peptide sequences which have an impact on cardiovascular health.

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.

Anxiolytic effects of ACE inhibitory peptides on the behavior of rats in an elevated plus-maze

Three novel egg white-derived peptides were demonstrated to display in vitro activities against the angiotensin converting enzyme (ACE).

Antioxidant and ACE Inhibitory Bioactive Peptides Purified from Egg Yolk Proteins

Protein by-products from the extraction of lecithin from egg yolk can be converted into value-added products, such as bioactive hydrolysates and peptides that have potential health enhancing antioxidant, and antihypertensive properties. In this study, the antioxidant and angiotensin converting enzyme (ACE) inhibitory activities of peptides isolated and purified from egg yolk protein were investigated. Defatted egg yolk was hydrolyzed using pepsin and pancreatin and sequentially fractionated by ultrafiltration, followed by gel filtration to produce egg yolk gel filtration fractions (EYGF). Of these, two fractions, EYGF-23 and EYGF-33, effectively inhibited the peroxides and thiobarbituric acid reactive substance (TBARS) in an oxidizing linoleic acid model system. The antioxidant mechanism involved superoxide anion and hydroxyl radicals scavenging and ferrous chelation. The presence of hydrophobic amino acids such as tyrosine (Y) and tryptophan (W), in sequences identified by LC-MS as WYGPD (EYGF-23) and KLSDW (EYGF-33), contributed to the antioxidant activity and were not significantly different from the synthetic BHA antioxidant. A third fraction (EYGF-56) was also purified from egg yolk protein by gel filtration and exhibited high ACE inhibitory activity (69%) and IC₅₀ value (3.35 mg/mL). The SDNRNQGY peptide (10 mg/mL) had ACE inhibitory activity, which was not significantly different from that of the positive control captopril (0.5 mg/mL). In addition, YPSPV in (EYGF-33) (10 mg/mL) had higher ACE inhibitory activity compared with captopril. These findings indicated a substantial potential for producing valuable peptides with antioxidant and ACE inhibitory activity from egg yolk.

Activity prediction and molecular mechanism of bovine blood derived angiotensin I-converting enzyme inhibitory peptides

Development of angiotensin I-converting enzyme (ACE, EC 3.4.15.1) inhibitory peptides from food protein is under extensive research as alternative for the prevention of hypertension. However, it is difficult to identify peptides released from food sources. To accelerate the progress of peptide identification, a three layer back propagation neural network model was established to predict the ACE-inhibitory activity of pentapeptides derived from bovine hemoglobin by simulated enzyme digestion. The pentapeptide WTQRF has the best predicted value with experimental IC50 23.93 μM. The potential molecular mechanism of the WTQRF / ACE interaction was investigated by flexible docking.

Bioactive peptides from egg: a review

Purpose

– The aim of the article was to focus on various peptides identified in the egg and their probable application as novel ingredients in the development of functional food products. Bioactive peptides of egg origin have attracted increasing interest as one of the prominent candidates for development of various health-promoting functional and designer foods.

Design/methodology/approach

– Traditionally known as a source of highly valuable proteins in human nutrition, eggs are nowadays also considered as an important source of many bioactive peptides which may find wide application in medicine and food production. These specific protein fragments from egg proteins which, above and beyond their nutritional capabilities, have a positive impact on the body’s function or condition by affecting the digestive, endocrine, cardiovascular, immune and nervous systems, and may ultimately influence health.

Findings

– Several peptides that are released in vitro or in vivo from egg proteins have been attributed to different health effects, including antihypertensive effects, antimicrobial properties, antioxidant activities, anticancer activity, immunomodulating activity, antiadhesive properties and enhancement of nutrient absorption and/or bioavailability. Extensive research has been undertaken to identify and characterize these biologically active peptides of egg origin which has changed the image of egg as a new source of biologically active ingredients for the development of functional foods with specific benefits for human health and treatment and prevention of diseases.

Originality/value

– The paper mainly describes the above-stated properties of bioactive peptides derived from egg proteins.

Beneficial effects of simulated gastro-intestinal digests of fried egg and its fractions on blood pressure, plasma lipids and oxidative stress in spontaneously hypertensive rats

Background

We have previously characterized several antihypertensive peptides in simulated digests of cooked eggs and showed blood pressure lowering property of fried whole egg digest. However, the long-term effects of this hydrolysate and its fractions on blood pressure are not known. Therefore, the objectives of the study were to determine the effects of long term administration of fried whole egg hydrolysate and its fractions (i.e. egg white and egg yolk) on regulation of blood pressure and associated factors in cardiovascular disease such as plasma lipid profile and tissue oxidative stress.

Methods and Results

We used spontaneously hypertensive rats (SHR), an animal model of essential hypertension. Hydrolysates of fried egg and its fractions were prepared by simulated gastro-intestinal digestion with pepsin and pancreatin. 16–17 week old male SHRs were orally administered fried whole egg hydrolysate, non-hydrolyzed fried whole egg, egg white hydrolysate or egg yolk hydrolysates (either defatted, or not) daily for 18 days. Blood pressure (BP) and heart rate were monitored by telemetry. Animals were sacrificed at the end of the treatment for vascular function studies and evaluating plasma lipid profile and tissue oxidative stress. BP was reduced by feeding fried whole egg hydrolysate but not by the non-hydrolyzed product suggesting a critical role for in vitro digestion in releasing anti-hypertensive peptides. Egg white hydrolysate and defatted egg yolk hydrolysate (but not egg yolk hydrolysate) also had similar effects. Reduction in BP was accompanied by the restoration of nitric oxide (NO) dependent vasorelaxation and reduction of plasma angiotensin II. Fried whole egg hydrolysate also reduced plasma levels of triglyceride although it was increased by the non-hydrolyzed sample. Additionally the hydrolyzed preparations attenuated tissue oxidative stress.

Conclusion

Our results demonstrate that fried egg hydrolysates exert anti-hypertensive effects, improve plasma lipid profile and attenuate tissue oxidative stress in vivo.

Application and bioactive properties of proteins and peptides derived from hen eggs: opportunities and challenges

Several proteins and peptides that are released in vitro and/or in vivo from hen eggs are biologically active and have a variety of functional properties in humans beyond normal nutrition, for which extensive studies have been performed. This review focuses on their biological activities, including antihypertensive, antioxidant, antimicrobial, antiadhesive, immunomodulatory and antithrombotic activities and enhancement of mineral absorption. These proteins and peptides have been shown to regulate the nervous system, cardiovascular system, immune system and gastrointestinal system. The potential application and future directions of research on these bioactive peptides and proteins in the food industry are also addressed.

Pilot-scale production of soybean oligopeptides and antioxidant and antihypertensive effects in vitro and in vivo

Soybean oligopeptides (SOP) with low molecular weights were prepared by two-step enzymatic hydrolysis on a pilot-scale. Peptide and free amino acid contents of SOP were 82.5 ± 1.13 % and 3.7 ± 0.28 % respectively. The molecular weight distribution of SOP was mainly bellow 1,000 Da (85.4 %), 56.7 % of which were 140-500 Da. SOP showed strong stability to proteolytic digestion by pepsin and trypsin. The antioxidant activities and in vitro and in vivo antihypertensive effects of SOP were evaluated. Results showed that SOP exhibited 1,1-diphenyl-2-picrylhydrazyl radical scavenging effect (IC50 = 4.5 ± 0.13 mg/mL), and significantly inhibited lipid peroxidation in linoleic acid oxidation system (IC50 = 1.2 ± 0.09 mg/mL). SOP had potent angiotensin I-converting enzyme inhibitory activity (IC50 = 1.1 ± 0.06 mg/mL), and antihypertensive effect in spontaneously hypertensive rats at a dose of 200 mg/kg. This study indicated that SOP could be a natural antioxidative or antihypertensive compound in the medicine and food industries.

Transport of Egg White ACE-Inhibitory Peptide, Gln-Ile-Gly-Leu-Phe, in Human Intestinal Caco-2 Cell Monolayers with Cytoprotective Effect

The purpose of this study was to investigate the transepithelial transport and cytoprotective effect of Gln-Ile-Gly-Leu-Phe (QIGLF), an ACE-inhibitory peptide derived from egg white ovalbumin, in human intestinal Caco-2 cell monolayers. The results showed that QIGLF could be absorbed intact through Caco-2 cell monolayers with a P_app value of (9.11 ± 0.19) × 10^-7 cm/s (transport kinetic parameters: K_m, 32.37 ± 12.59 mM; V_max, 1.23 ± 0.49 μM/min cm²). The transport was not significantly decreased by sodium azide and Gly-Pro, an ATP synthesis inhibitor and a peptide transporter 1 (PepT1) substrate, respectively, suggesting that transport of QIGLF was not energy-dependent and carrier-mediated. In addition, wortmannin, a transcytosis inhibitor, had little effect on the transport, suggesting that endocytosis was not involved in the transport of QIGLF. However, the transport of QIGLF was increased significantly in the presence of cytochalasin D, a tight junction disruptor, suggesting that paracellular transport via tight junctions was the major transport mechanism for intact QIGLF across Caco-2 cell monolayers. Moreover, QIGLF was added to Caco-2 cells followed by addition of H₂O₂, and exhibited significant cytoprotective effect in Caco-2 cells against oxidative stress induced by H₂O₂.