A new method for determination of antithrombotic activity of egg white protein hydrolysate by microplate reader

Fermented milks with specific Lactobacillus spp. with potential cardioprotective effects

In vitro and in vivo studies have reported the potential cardioprotective effects of fermented milks (FM). The aim of the present study was to evaluate the inhibitory activities of angiotensin converting enzyme (ACE), thrombin enzyme (TI) and micellar solubility of cholesterol of FM after 24 and 48 h of fermentation with Limosilactobacillus fermentum (J20, J23, J28 and J38), Lactiplantibacillus plantarum (J25) or Lactiplantibacillus pentosus (J34 and J37) exposed to simulated gastrointestinal digestion. Results showed that FM with J20 and J23 at 48 h of fermentation presented significantly (p < 0.05) higher degree of hydrolysis than other FM, and were not significantly different (p > 0.05) between them. Conversely, peptide relative abundance was significantly (p < 0.05) higher in FM with J20 than FM with J23. Moreover, IC₅₀ (protein concentration necessary to inhibit enzyme activity by 50%) for ACE inhibition were 0.33 and 0.5 mg/mL for FM with J20 and J23, respectively. For TI inhibition, the IC₅₀ were 0.3 and 0.24 mg/mL for FM with J20 and J23, respectively. Results exhibited 51 and 74% inhibition of micellar solubility cholesterol for FM with J20 and J23, respectively. Therefore, these results showed that not only peptide abundance, but also specific peptides might be responsible for these potential cardioprotective effects.

Anticoagulant Dodecapeptide Suppresses Thrombosis In Vivo by Inhibiting the Thrombin Exosite-I Binding Site

Thrombin is a crucial regulatory serine protease in hemostasis and thrombosis and has been a therapeutic target of thrombotic events. A novel oyster-derived thrombin inhibitory dodecapeptide (IEELEELEAER, P-2-CG) was identified and characterized. P-2-CG prolonged thrombin time from 9.6 s to 23.3 s at 5 mg/mL in vitro. P-2-CG bound to thrombin Exosite-I domain spontaneously. The occupied Exosite-I blocked fibrinogen binding, which prolonged fibrinogen clotting time to 28 s from 18.5 s. Molecule dynamics demonstrated the interaction of P-2-CG and thrombin Exosite-I involved in eight hydrogen bonds and lots of electrostatic forces. The residue Tyr⁷⁶ at thrombin Exosite-I is one critical amino acid for fibrinogen binding. The Glu¹¹ in P-2-CG was bound with Tyr⁷⁶ through strong hydrogen bonds and hydrophobic action. P-2-CG also significantly reduced the mortality of mice that suffered an acute pulmonary embolism induced by thrombin and inhibited mice tail thrombosis induced by κ-carrageenan. The thrombin inhibitory efficiency in vitro and antithrombosis in vivo of P-2-CG provided insight for further applications to serve as an antithrombotic agent.

Isothermal Self-Primer EXPonential Amplification Reaction (SPEXPAR) for Highly Sensitive Detection of Single-Stranded Nucleic Acids and Proteins

Development of versatile sensing methods for sensitive and specific detection of clinically relevant nucleic acids and proteins is of great value for disease monitoring and diagnosis. In this work, we propose a novel isothermal Self-primer EXPonential Amplification Reaction (SPEXPAR) strategy based on a rationally engineered structure-switchable Metastable Hairpin template (MH-template). The MH-template initially keeps inactive with its self-primer overhanging a part of target recognition region to inhibit polymerization. The present targets can specifically compel the MH-template to transform into an "activate" conformation that primes a target-recyclable EXPAR. The method is simple and sensitive, can accurately and facilely detect long-chain single-stranded nucleic acids or proteins without the need of exogenous primer probes, and has a high amplification efficiency theoretically more than 2ⁿ. For a proof-of-concept demonstration, the SPEXPAR method was used to sensitively detect the characteristic sequence of the typical swine fever virus (CSFV) RNA and thrombin, as nucleic acid and protein models, with limits of detection down to 43 aM and 39 fM, respectively, and even the CSFV RNA in attenuated vaccine samples and thrombin in diluted serum samples. The SPEXPAR method may serve as a powerful technique for the biological research of single-stranded nucleic acids and proteins.

Isolation and characterization of oligopeptides with vascular disease suppression effects derived from wheat gluten

Wheat gluten was hydrolyzed with both alkaline protease and neutral protease to produce high-protein and low-wheat-weight oligopeptides (WOP), which was subjected to a multistage purification. Then, high performance liquid chromatography was applied to separate WOP. In order to identify WOP sequences, six major fractions were gathered for mass spectrometry. A total of 15 peptides were synthesized for further in vitro analyses of their antithrombotic activity, vasorelaxation activity, and cholesterol reducing activity. Two antithrombotic peptides (ILPR and ILR), three vasorelaxant peptides (VN, FPQ, and FR), and four cholesterol-lowering peptides (QRQ, ILPR, FPQ, and ILR) were identified. These active peptides in WOP were also quantified. These peptides are novel candidate peptides with vascular disease suppressing effects. The results indicate WOP as good protein sources for multifunctional peptides.

VITPOR AI, A Coagulation Factor XIIa Inhibitor from Porphyra yezoensis: In Vivo Mode of Action and Assessment of Platelet Function Analysis

BACKGROUND

Thrombosis represents as the prime contributor to the burden of diseases, worldwide. Conventional anticoagulants for thrombosis therapy have a common bleeding side effect. Bioactive peptides are studied to be an effective alternative for currently available therapeutic drugs.

OBJECTIVE

In this study, VITPOR AI peptide, a previously reported coagulation FXIIa inhibitor from Nori (Porphyra yezoensis), was assessed for its inhibitory activity against FXIIa and its in vivo mode of action.

METHODS

In vivo efficacy as well as the antithrombotic property of the peptide was evaluated in mice model by ex vivo activated Partial Thromboplastin Time assay, tail transection model and whole blood clotting time. The enzyme kinetics was studied using chromogenic substrate assay.

RESULTS

The kinetic behaviour of VITPOR AI showed that the peptide is a competitive inhibitor of FXIIa. Peptide showed significant inhibition of platelet adhesion and aggregation. VITPOR AI exhibited significant antithrombotic activity. Furthermore, ex vivo activated Partial Thromboplastin Time assay revealed that VITPOR AI exhibited potent anticoagulant activity in vivo. Tail bleeding assay revealed that the peptide did not prolong bleeding time in mice even at a higher dose of 5 mg/kg. Cytotoxicity studies of the peptide against human blood leukocytes indicated the safety of the peptide.

CONCLUSION

VITPOR AI could be prospected as a potent anticoagulant with Factor XIIa inhibition, antiplatelet aggregation and antithrombotic activity. It was also studied to have no bleeding side effect.

Low-molecular-weight peptides with potential cardiovascular regulatory functions from Atlantic salmon skin

Salmon skin collagen peptides (SSCPs) have potential for improving physiological conditions such as early alcoholic liver injury, type 2 diabetes and hypertension. Here, we focused on thein vitroeffects of SSCPs on vascular function. For the production of SSCPs, alcalase and papain were used to hydrolyse the skin of Atlantic salmon (Salmo salarL.), and their separation was made by reverse-phase high performance liquid chromatography. There were 10 low-molecular-weight peptides newly identified by mass spectrometry. In addition to five peptides previously identified, a total of 15 peptides were applied to anin vitroanalysis of cholesterol-reducing, vasorelaxant and antithrombotic activities. The results showed that the SSCPs contained six cholesterol-lowering peptides (Ala-Pro, Leu-Gln, Asn-Val-Gly, Arg-Glu-Arg, Pro-His and Gly-Pro-Arg), two vasorelaxant peptides (Leu-Gln and Pro-His), and four antithrombotic peptides (Gly-Pro-Arg, Arg-Glu-Arg, Val-Asp-Gly-Lys and Val-Arg) as novel candidate peptides with beneficial effects on vascular function. These active peptides were also quantified. This study reveals that several peptides from salmon skin possess bifunctional properties.

A novel heptapeptide derived from Crassostrea gigas shows anticoagulant activity by targeting for thrombin active domain

A novel food-derived anticoagulant heptapeptides (P-3-CG) was isolated and characterized from oyster (Crassostrea gigas) pepsin hydrolysate. P-3-CG competed with fibrinogen against thrombin active domain by a spontaneous and exothermic reaction which was entropically driven. The residue Lys7 of P-3-CG anchored thrombin S₁ pocket strongly, which inhibited fibrinogen binding to the thrombin, then blocked the conversion of fibrinogen to fibrin. The fibrinogen clotting time was prolonged to 27.55 s, and the reciprocally authenticated results of dynamic light scattering and scanning electron microscope further explained for fibrinogen clotting time extension. Inhibition of amidolytic activity of thrombin was affected significantly by reaction time and P-3-CG concentration. Furthermore, P-3-CG prolonged activated partial thromboplastin time significantly in vitro/vivo, and decreased the mortality which was confirmed by pulmonary pathological slide results. The obtained results demonstrated that P-3-CG may potentially serve as an alternative food-derived anticoagulant peptide that could be utilized for thrombosis prevention.

Investigations in ultrasound-assisted anticoagulant production by marine Bacillus subtilis ZHX

Anticoagulants are the main drugs for the prevention and treatment of thromboembolism. However, most of the present anticoagulants have shortcomings and novel anticoagulants are in great demand. Marine microorganisms are an important source of new drugs. Therefore, in this study, ultrasound was applied to enhance anticoagulant accumulation by marine Bacillus subtilis ZHX. Ultrasound parameters were optimized by single-factor experiments exploring the effects of ultrasound power, duration, duty cycle and the cell growth phases. The optimum conditions were exponential prophase (5 h) with 25 kHz frequency, 140 W power, and a 40% duty cycle for 5 min. The maximum anticoagulant activity (55.36 U/mL) was 1.73 times that of the control group, and the fermentation time was shortened by 3 h. Under optimal conditions, ultrasound increased the carbon utilization by Bacillus subtilis ZHX without significant changes in morphology, favoring cell growth and anticoagulant production. However, excessive ultrasound caused intracellular damage, which inhibited biomass accumulation, decreasing anticoagulant activity and even leading to cell rupture. This is the first report on the use of ultrasound to enhance anticoagulant production by Bacillus, and it provides useful information for scaling-up the process.

A novel thrombin inhibitory peptide discovered from leech using affinity chromatography combined with ultra-high performance liquid chromatography-high resolution mass spectroscopy

Thrombin (THR) inhibitors play an important role in the treatment of thrombotic diseases. This study established a THR-based bio-specific extraction coupled with affinity chromatography and ultra-high performance liquid chromatography-high resolution mass spectroscopy (UPLC-HR-MS) analysis method to screen and identify THR ligands in Leech. After evaluating the reliability of the screening method using positive control drug (hirudin), it was successfully used to screen the potential active constituents in leech. And a comprehensive analysis of the peptides in leech elution was performed by UPLC-HR-MS, a total of 34 peptides were identified. At the same time, anti-THR activity was explored and inferred by searching databases and published literature. As a result, six peptides were discovered to be potential active compounds in leech. Further, the six peptides were synthesized and in vitro enzymatic activity assay was performed. Finally, SYELPDGQVITIGNER was screened as an anti-THR peptide with an IC50 value of 255.75 µM and it was discovered for the first time from Whitmania pigra Whitman and Hirudo nipponica Whitman. The molecular docking study showed that THR inhibitory activity of the polypeptide was mainly attributed to the hydrogen bond interactions, van der Waals forces and electrostatic interactions interaction between polypeptide and THR. These results suggest that the polypeptide is a potential natural THR inhibitor that can be used as anticoagulant.

Mechanism and inhibition kinetics of peptide P13 as thrombin inhibitor

Excessive coagulation can easily lead to arterial and venous thrombosis, which is the main reason for the evolution of myocardial infarction and cerebrovascular accidents. As a key coagulation factor for the coagulation pathway, thrombin has become a remarkable target for the control of thrombosis. The synthesized peptide P13 with amino acid sequence of N-RGDAGFAGDDAPR was expected to be an inhibitor with higher antithrombotic activity. The results showed that the IC₅₀ (50% inhibition of thrombin activity) of the peptide P13 was determined by colorimetric method to be 115 µM. And enzyme kinetic experiments showed that P13 was a competitive inhibitor of thrombin with K_i = 106 µM. Fluorescence spectra and three-dimensional fluorescence showed that P13 could alter the secondary structure of thrombin and the microenvironment of certain chromogenic amino acids. P13 can spontaneously bind with thrombin exosite 1 in the form of 1:1 mainly through hydrogen bonding and van der Waals force. And the optimal docking mode of P13 and thrombin was revealed by molecular docking with "-CDOCKER_Energy" of 178.679 kcal mol^-1. This study revealed P13 may become a potential anticoagulant drug widely used after further studies in preclinical and clinical trials.

Identification and molecular mechanism of antithrombotic peptides from oyster proteins released in simulated gastro-intestinal digestion

In this study, oyster (Crassostrea gigas) proteins were digested under in vitro gastrointestinal conditions to screen potential antithrombotic peptides. The sequences of the released peptides in the intestinal digestion phase were identified by ultra-performance liquid chromatography coupled to quadrupole time-of-flight MS (UPLC-Q-TOF-MS/MS). According to the antithrombotic activity analysis, the inhibitory ratio of oyster peptides showed an increasing trend, reaching up to 35.80% for a digestion period of 4 h. The APTT (activated partial thromboplastin time) and TT (thromboplastin time) were increased by oyster peptides for human serum in vitro. Oyster peptides showed a competitive inhibition effect on thrombin, based on Lineweaver-Burk plot analysis. Molecular docking between the antithrombotic peptides and thrombin (PDB: ) was conducted using Discovery Studio 2017. Potential inhibitors against thrombin and the mechanism of antithrombotic activity were predicted using the algorithm of CDOCKER. There are fourteen potential antithrombotic peptides, whose affinity with thrombin is higher than that of hirudin, as indicated by the "-CDOCKER energy" score (181.491). Peptide LSKEEIEEAKEV is similar in sequence to thrombin inhibitors. The binding sites of potential antithrombotic peptides against thrombin at the S1 pocket were compared with hirudin variant-2 (GDFEEIPEEYLQ). In addition, the peptides containing the RG/RGD sequence were identified, which can be hydrolyzed by thrombin as a substrate. Consequently, the oyster peptides released in simulated gastrointestinal digestion probably inhibit thrombin in two ways, not only as the inhibitor against the active site, but also as the substrate of thrombin. These results maybe be attributed to the potentially strong antithrombotic activity in the human digestive system.

Interaction of the synthetic antithrombotic peptide P10 with thrombin: a spectroscopy study

Thrombin is a critical serine protease in the coagulation system and is widely used as a target protein for antithrombotics. Spectroscopic analysis is a simple and effective method that is used to study the interaction between small molecules and proteins. In this study, the interactions of a potential antithrombotic peptide AGFAGDDAPR (P10) with thrombin were investigated by fluorescence spectroscopy, UV-vis spectroscopy, circular dichroism, Fourier-transform infrared spectroscopy and Raman spectroscopy, respectively. The results showed that the peptide P10 bonded to thrombin via hydrogen bonding and van der Waals forces, resulting in fluorescence quenching. And, the secondary structure of thrombin changed, the β-sheet decreased, and the random coil increased. The peptide P10 bonded to proline and lysine, and changed the space structure of thrombin, resulting in inhibition of thrombin activity. The results contributed to exploration of the mechanism of this potential antithrombotic drug interaction with thrombin in order to provide a preliminary understanding of the pharmacodynamic properties of P10.

Food-derived antithrombotic peptides: Preparation, identification, and interactions with thrombin

Thromboembolism and its sequelae have been the leading causes of morbidity and mortality throughout the world. Food-derived antithrombotic peptides, as potential ingredients in health-promoting functional foods targeting thrombus, have attracted increasing attention because of their high biological activities, low toxicity, and ease of metabolism in the human body. This review presents the conventional workflow of preparation, isolation and identification of antithrombotic peptides from various kinds of food materials. More importantly, to analyze the antithrombotic effects and mechanism of antithrombotic peptides, methods for interaction of anticoagulant peptides and thrombin, the main participant in thrombosis, were analyzed from biochemistry, solution chemistry and crystal chemistry. The present study is intended to highlight the recent advances in research of food-derived antithrombotic peptide as a novel vehicle in the field of food science and nutrition. Future outlooks are highlighted with the aim to suggest a research line to be followed in further studies with the introduced research approach.

Meta-Analysis for Correlating Structure of Bioactive Peptides in Foods of Animal Origin with Regard to Effect and Stability

Amino acid (AA) sequences of 807 bioactive peptides from foods of animal origin were examined in order to correlate peptide structure with activity (antihypertensive, antioxidative, immunomodulatory, antimicrobial, hypolipidemic, antithrombotic, and opioid) and stability in vivo. Food sources, such as milk, meat, eggs, and marine products, show different frequencies of bioactive peptides exhibiting specific effects. There is a correlation of peptide structure and effect, depending on type and position of AA. Opioid peptides contain a high percentage of aromatic AA residues, while antimicrobial peptides show an excess of positively charged AAs. AA residue position is significant, with those in the first and penultimate positions having the biggest effects on peptide activity. Peptides that have activity in vivo contain a high percentage (67%) of proline residues, but the positions of proline in the sequence depend on the length of the peptide. We also discuss the influence of processing on activity of these peptides, as well as methods for predicting release from the source protein and activity of peptides.

Identification and In Silico Prediction of Anticoagulant Peptides from the Enzymatic Hydrolysates of Mytilus edulis Proteins

Mytilus edulis is a typical marine bivalve mollusk. Many kinds of bioactive components with nutritional and pharmaceutical activities in Mytilus edulis were reported. In this study, eight different parts of Mytilus edulis tissues, i.e., the foot, byssus, pedal retractor muscle, mantle, gill, adductor muscle, viscera, and other parts, were separated and the proteins from these tissues were prepared. A total of 277 unique peptides from the hydrolysates of different proteins were identified by UPLC-Q-TOF-MS/MS, and the molecular weight distribution of the peptides in different tissues was investigated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The bioactivity of the peptides was predicted through the Peptide Ranker database and molecular docking. Moreover, the peptides from the adductor muscle were chosen to do the active validation of anticoagulant activity. The active mechanism of three peptides from the adductor muscle, VQQELEDAEERADSAEGSLQK, RMEADIAAMQSDLDDALNGQR, and AAFLLGVNSNDLLK, were analyzed by Discovery Studio 2017, which also explained the anticoagulant activity of the hydrolysates of proteins from adductor muscle. This study optimized a screening and identification method of bioactive peptides from enzymatic hydrolysates of different tissues in Mytilus edulis.

Size exclusion chromatography (SEC-HPLC) as an alternative to study thrombin inhibition

In vitro analysis of anticoagulant compounds with a potential use as antithrombotic drugs, has been traditionally performed using techniques like spectrophotometry, turbidimetry, as well as electrochemical and clinical assays. Although, these techniques have some disadvantages such as: the inability to measure the total biological activity of thrombin, interferences and, sometimes, the quantitative determination of the inhibition ratio is not accurate. In the present work, the conversion of fibrinogen to fibrin was monitored by molecular exclusion chromatography (SEC-HPLC) in three different reaction systems. An inhibition percentage of 43.19±2.02% was obtained using heparin as an anticoagulant, in addition to the determination of the percentage of heparin bonded to thrombin. This methodology has not been previously described and has high potential for the determination of anticoagulant capacity with higher precision, the determination of thrombin's total biological activity and the quantitative determination of the inhibition ratio.

Identification and Antithrombotic Activity of Peptides from Blue Mussel (Mytilus edulis) Protein

The blue mussel (Mytilus edulis) reportedly contains many bioactive components of nutritional value. Water-, salt- and acid-soluble M. edulis protein fractions were obtained and the proteins were trypsinized. The resultant peptides were analyzed by ultra-performance liquid chromatography quadrupole time of flight tandem mass spectrometry (UPLC-Q-TOF-MS/MS). 387 unique peptides were identified that matched 81 precursor proteins. Molecular mass distributions of the proteins and peptides were analyzed by sodium dodecyl sulfate-polyacryl amide gel electrophoresis (SDS-PAGE). The differences between the three protein samples were studied by Venn diagram of peptide and protein compositions. Toxicity, allergic and antithrombotic activity of peptides was predicted using database website and molecular docking respectively. The antithrombotic activity of enzymatic hydrolysate from water-, salt- and acid-soluble M. edulis protein were 40.17%, 85.74%, 82.00% at 5 mg/mL, respectively. Active mechanism of antithrombotic peptide (ELEDSLDSER) was also research about amino acid binding sites and interaction, simultaneously.

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.

Antithrombotic and Antioxidant Activity of Amaranth Hydrolysate Obtained by Activation of an Endogenous Protease

Ingestion of diets with antithrombotic and antioxidant components offer a convenient and effective way to prevent and reduce the incidence of cardiovascular diseases. The aim of the present work was to obtain an amaranth hydrolysate by the activation of an endogenous aspartic protease, to establish adequate experimental conditions, and to evaluate its antithrombotic and antioxidant activity in order to assess its potential application as an ingredient in functional foods. The results obtained not only confirmed the presence of an endogenous protease in the amaranth isolate, but also allowed us to select an adequate incubation conditions (pH 2, 40 °C, 16 h). The hydrolysate obtained (degree of hydrolysis 5.3 ± 0.4 %) showed potential antithrombotic activity (IC50 = 5.9 ± 0.1 mg soluble protein/mL) and had more antioxidant activity than the isolate, indicating that the activation of the protease released bioactive peptides from amaranth proteins. Decreasing the pH is a simple and cheap process and is another way to obtain potential functional ingredients with bioactive compounds.

Antithrombotic Effects of Amaranthus hypochondriacus Proteins in Rats

Cardiovascular disease (CVD) is a major cause of disability and premature death throughout the world. Diets with antithrombotic components offer a convenient and effective way of preventing and reducing CVD incidence. The aim of the present work was to assess in vivo and ex vivo effects of Amaranthus hypochondriacus proteins on platelet plug formation and coagulation cascade. Amaranth proteins were orally administrated to rats (AG, 8 animals) and bleeding time was determined showing no significant difference compared with control rats (CG, 7 animals). However, results show a strong tendency, suggesting that amaranth proteins are involved in the inhibition of thrombus formation. Non-anticoagulated blood extracted from animals was analyzed with the hemostatometer, where AG parameters obtained were twice the values showed by CG. The clotting tests, thrombin time (TT) and activated partial thromboplastin time (APTT), presented a 17 and 14% clotting formation increase respectively when comparing AG with CG. The ex-vivo assays confirm the hypothesis inferring that amaranth proteins are a potential antithrombotic agent.

Isolation and identification of a novel anticoagulant peptide from enzymatic hydrolysates of scorpion (Buthus martensii Karsch) protein

An enzymatic hydrolysis approach was proposed for the preparation of bioactive hydrolysate of scorpion Buthus martensii Karsch (BmK) protein. Results showed that the anticoagulant activity of the hydrolysates of BmK protein was closely related to both the enzyme type and the degree of hydrolysis. Alcalase AF showed to be the best enzymes for the hydrolysis. And the hydrolysis degree (DH) was closely related with the anticoagulant activity of the hydrolyzate. At a DH value of 18% with Alcalase AF, the hydrolyzate exhibited the highest activity. The hydrolysate was then separated and purified by consecutive chromatographic procedures, giving a novel anticoagulant peptide consisting of ten amino acids (MW: 1119.8Da) with its sequence of Val-Glu-Pro-Val-Thr-Val-Asn-Pro- His-Glu identified by MALDI-TOF/TOF MS. The negatively charged amino acids and hydrophobic amino acids may contribute to the anticoagulant activity of the prepared peptides. And the Val residue in N-terminal was also critical for the anticoagulant activity of the BmK peptide. Furthermore, the anticoagulant activity kept stable after in vitro digestive simulation. This research provided a promising bioprocessing route for production of anticoagulant peptides using BmK protein as a potentially valuable bioresource.

Structure elucidation of ACE-inhibitory and antithrombotic peptides isolated from mackerel skin gelatine hydrolysates

BACKGROUND

The fish-processing industry generates significant amounts of waste and by-products that are usually discarded. This study investigated the preparation of bioactive gelatine peptides from fish skin. Gelatine was extracted from mackerel (Scomber scombrus) skin and hydrolysed by pepsin for 1, 2, 6 and 24 h. All hydrolysates were screened for antioxidant, ACE-inhibitory and antithrombotic activities.

RESULTS

Gelatine peptides obtained after 24 h of hydrolysis exhibited the highest antioxidant activity (DPPH reduction ∼80%, FRAP ∼130 µmol Trolox equivalent L(-1) ). These hydrolysates had high ACE-inhibitory activity (>70%) and were able to significantly (P < 0.05) inhibit platelet aggregation by about 30%, corresponding to moderate antithrombotic activity.

CONCLUSION

The bioactive properties were mainly due to the presence of low-molecular-weight peptides of 337 and 423 Da.

Preventive effect of fermented Maillard reaction products from milk proteins in cardiovascular health

The aim of this study was to determine the dual effect of Maillard reaction and fermentation on the preventive cardiovascular effects of milk proteins. Maillard reaction products (MRP) were prepared from the reaction between milk proteins, such as whey protein concentrates (WPC) and sodium caseinate (SC), and lactose. The hydrolysates of MRP were obtained from fermentation by lactic acid bacteria (LAB; i.e., Lactobacillus gasseri H10, L. gasseri H11, Lactobacillus fermentum H4, and L. fermentum H9, where human-isolated strains were designated H1 to H15), which had excellent proteolytic and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities (>20%). The antioxidant activity of MRP was greater than that of intact proteins in assays of the reaction with 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt and trivalent ferric ions; moreover, the effect of MRP was synergistically improved by fermentation. The Maillard reaction dramatically increased the level of antithrombotic activity and 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) inhibitory effect of milk proteins, but did not change the level of activity for micellar cholesterol solubility. Furthermore, specific biological properties were enhanced by fermentation. Lactobacillus gasseri H11 demonstrated the greatest activity for thrombin and HMGR inhibition in Maillard-reacted WPC, by 42 and 33%, respectively, whereas hydrolysates of Maillard-reacted SC fermented by L. fermentum H9 demonstrated the highest reduction rate for micellar cholesterol solubility, at 52%. In addition, the small compounds that were likely released by fermentation of MRP were identified by size-exclusion chromatography. Therefore, MRP and hydrolysates of fermented MRP could be used to reduce cardiovascular risks.

Proteomics analysis of egg white proteins from different egg varieties

The market of specialty eggs, such as omega-3-enriched eggs, organic eggs, and free-range eggs, is continuously growing. The nutritional composition of egg yolk can be manipulated by feed diet; however, it is not known if there is any difference in the composition of egg white proteins among different egg varieties. The purpose of the study was to compare the egg white proteins among six different egg varieties using proteomics analysis. Egg white proteins were analyzed using two-dimensional gel electrophoresis (2-DE), and 89 protein spots were subjected to LC-MS/MS. A total of 23 proteins, belonging to Gallus gallus , were identified from 72 detected protein spots. A quiescence-specific protein precursor in egg white was identified for the first time in this study. Significant differences in the abundant levels of 19 proteins (from 65 protein spots) were observed among six egg varieties. Four proteins, ovalbumin-related protein Y, cystatin, avidin, and albumin precursor, were not different among these six egg varieties. These findings suggest that the abundance, but not the composition, of egg white proteins varied among the egg varieties.