Recovery of a novel Ca-binding peptide from Alaska Pollack (Theragra chalcogramma) backbone by pepsinolytic hydrolysis

Evaluating the capability of soybean peptides as calcium ion carriers: a study through sequence analysis and molecular dynamics simulations

Calcium homeostasis imbalance in the body can lead to a variety of chronic diseases. Supplement efficiency is essential. Peptide calcium chelate, a fourth-generation calcium supplement, offers easy absorption and minimal side effects. Its effectiveness relies on peptide's calcium binding capacity. However, research on amino acid sequences in peptides with high calcium binding capacity (HCBC) is limited, affecting the efficient identification of such peptides. This study used soybean peptides (SP), separated and purified by gel chromatography, to obtain HCBC peptide (137.45 μg mg-1) and normal peptide (≤95.78 μg mg-1). Mass spectrometry identified the sequences of these peptides, and an analysis of the positional distribution of characteristic amino acids followed. Two HCBC peptides with sequences GGDLVS (271.55 μg mg-1) and YEGVIL (272.54 μg mg-1) were discovered. Molecular dynamics showed that when either aspartic acid is located near the N-terminal's middle, or glutamic acid is near the end, or in cases of continuous Asp or Glu, the binding speed, probability, and strength between the peptide and calcium ions are superior compared to those at other locations. The study's goal was to clarify how the positions of characteristic amino acids in peptides affect calcium binding, aiding in developing peptide calcium chelates as a novel calcium supplement.

Novel iron-chelating peptide from egg yolk: Preparation, characterization, and iron transportation

In this work, an egg yolk protein hydrolysate (EYPH) with a high iron-chelating ability (87.32%) was prepared. The fractionation using 60% (v/v) ethanol concentration (E3 fraction) led to the efficiently accumulating the iron-chelating peptides in EYPH. The characterization results showed that iron mainly chelated with carboxyl, amino and phosphate groups of peptides. From E3 fraction, six iron-chelating peptides with MW ranging from 1372.36 to 2937.04 Da were identified and a hypothesized molecular model of DDSSSpSpSpSpSpSVLSK-Fe was simulated. In vitro stability determination showed that E3-Fe chelate owned a good heat, alkalinity and digestion tolerance, but a relatively bad acid tolerance. Finally, iron transport analysis showed that iron in the E3-Fe would be absorbed in caco-2 cell membrane more effectively than that of iron salts, indicating that it was possible to apply the E3-Fe complex as iron supplements.

Isolation, characterization, and molecular docking analyses of novel calcium-chelating peptide from soy yogurt and the study of its calcium chelation mechanism

BACKGROUND

Calcium is an essential dietary mineral nutrient for humans. Digestive instability limits the bioavailability of calcium ions. Peptide-calcium chelate has been proven to excite higher calcium absorption than amino acid-calcium chelate, organic and inorganic calcium. Soy yogurt, which is produced via liquid-state fermentation using lactic acid bacteria, has a high amount of bioavailable calcium. In this study, a novel peptide with high calcium binding affinity was purified and identified from soy yogurt. The binding mechanism of peptide and calcium was then analyzed by bioinformatics and spectral analysis. Furthermore, the effect of the novel peptide on gastrointestinal stability by the Caco-2 cell model and calcium bioavailability in vivo were investigated by the zebrafish model.

RESULTS

The results showed that a novel peptide was purified and identified as DEDEQIPSHPPR (CBP). Calcium ions probably coordinate with Glu-2 and Glu-4 carboxyl groups via salt bridges and interact with Asp-1, Asp-3, and Arg-12 in CBP via charge pairing. The calcium binding activity of the CBP was 36.64 ± 0.04 mg g^-1 . Fourier transform infrared (FTIR) spectra showed that calcium spontaneously bound to the amino group nitrogen and oxygen atoms of the carboxyl group. The binding mode is either bidentate or unidentate, depending on the circumstances. More importantly, the CBP peptide substantially increased the bone mass in a zebrafish osteoporosis model.

CONCLUSION

The more glutamic acid and aspartic acid, the high was the calcium affinity with peptide. Soy yogurt-derived peptides can be used as carriers of calcium ions throughout the gastrointestinal tract, which may be clinically useful for osteoporosis therapy. © 2022 Society of Chemical Industry.

Metal-Chelating Peptides Separation Using Immobilized Metal Ion Affinity Chromatography: Experimental Methodology and Simulation

Metal-Chelating Peptides (MCPs), obtained from protein hydrolysates, present various applications in the field of nutrition, pharmacy, cosmetic etc. The separation of MCPs from hydrolysates mixture is challenging, yet, techniques based on peptide-metal ion interactions such as Immobilized Metal Ion Affinity Chromatography (IMAC) seem to be efficient. However, separation processes are time consuming and expensive, therefore separation prediction using chromatography modelling and simulation should be necessary. Meanwhile, the obtention of sorption isotherm for chromatography modelling is a crucial step. Thus, Surface Plasmon Resonance (SPR), a biosensor method efficient to screen MCPs in hydrolysates and with similarities to IMAC might be a good option to acquire sorption isotherm. This review highlights IMAC experimental methodology to separate MCPs and how, IMAC chromatography can be modelled using transport dispersive model and input data obtained from SPR for peptides separation simulation.

The Formation, Structural Characteristics, Absorption Pathways and Bioavailability of Calcium–Peptide Chelates

Calcium is one of the most important mineral elements in the human body and is closely related to the maintenance of human health. To prevent calcium deficiency, various calcium supplements have been developed, but their application tends to be limited by low calcium content and highly irritating effects on the stomach, among other side effects. Recently, calcium–peptide chelates, which have excellent stability and are easily absorbed, have received attention as an alternative emerging calcium supplement. Calcium-binding peptides (CaBP) are usually obtained via the hydrolysis of animal or plant proteins, and calcium-binding capacity (CaBC) can be further improved through chromatographic purification techniques. In calcium ions, the phosphate group, carboxylic group and nitrogen atom in the peptide are the main binding sites, and the four modes of combination are the unidentate mode, bidentate mode, bridging mode and α mode. The stability and safety of calcium–peptide chelates are discussed in this paper, the intestinal absorption pathways of calcium elements and peptides are described, and the bioavailability of calcium–peptide chelates, both in vitro and in vivo, is also introduced. This review of the research status of calcium–peptide chelates aims to provide a reasonable theoretical basis for their application as calcium supplementation products.

Production of Collagens and Protein Hydrolysates with Antimicrobial and Antioxidant Activity from Sheep Slaughter By-Products

This work aimed to produce collagens and hydrolysates with antimicrobial and antioxidant activity from sheep slaughter by-products. The by-products (sheep and lamb) were treated and extracted. The collagens were hydrolyzed with the enzyme Alcalase^®. The spectra of collagens and hydrolysates were similar (amide bands I, II, III, A, B). The bands presented by the collagens (α₁, α₂, β) were characteristic of type I collagen. The hydrolysates showed molecular weight peptides equal to/lower than 15 kDa. Collagens had a denaturation temperature of 39.32 (lamb) and 36.38 °C (sheep), whereas the hydrolysates did not undergo thermal transition. Hydrolysates showed lower values of antioxidant activity (AA) than the collagens. The collagens from lamb and from sheep displayed an AA of 13.4% (concentration of 0.0002%) and 13.1% (concentration of 0.0005%), respectively. At the concentration of 0.0020%, the lamb hydrolysates displayed an AA of 10.2%, whereas the sheep hydrolysates had an AA of only 1.98%. Collagen also showed higher antimicrobial activity compared to hydrolysates, requiring a lower concentration to inhibit the microorganisms tested. Sheep slaughter by-products proved to be a viable source for obtaining protein hydrolysates and collagens with antimicrobial and antioxidant activity, which can be applied in the development of nutraceuticals beneficial to human health.

Theragra chalcogramma Hydrolysates, Rich in Gly-Leu-Pro-Ser-Tyr-Thr, Exerts Anti-Photoaging Potential via Targeting MAPK and NF-κB Pathways in SD Rats

Previous studies have revealed that excessive exposure to UV irradiation is the main cause of skin photoaging and the signaling pathways of MAPK and NF-κB are involved in this progression. The present study aims to investigate the anti-photoaging effects of low molecular weight hydrolysates from Theragra chalcogramma (TCH) and to clarify the underlying mechanism. The degradation of mechanical barrier functions in photoaged skin was substantially ameliorated after TCH administration; meanwhile, TCH significantly elevated the antioxidant capacity and suppressed the over-production of inflammatory cytokine IL-1β. Moreover, the histopathological deteriorations such as epidermal hyperplasia and dermal loss were significantly alleviated, along with the increase in procollagen type I content and decrease in MMP-1 activity (p < 0.05). Furthermore, TCH effectively blocked the MAPK and NF-κB signaling pathways through inhibition of the phosphorylation of p38, JNK, ERK, iκB, and p65 proteins. Collectively, these data indicate that TCH has potential as a novel ingredient for the development of anti-photoaging foods.

Marine Products As a Promising Resource of Bioactive Peptides: Update of Extraction Strategies and Their Physiological Regulatory Effects

Marine products are a rich source of nutritional components and play important roles in promoting human health. Fish, mollusks, shellfish, as well as seaweeds are the major components of marine products with high-quality proteins. During the last several decades, bioactive peptides from marine products have gained much attention due to their diverse biological properties including antioxidant, antihypertensive, antimicrobial, antidiabetic, immunoregulation, and antifatigue. The structural characteristics of marine bioactive peptides largely determine the differences in signaling pathways that can be involved, which is also an internal mechanism to exert various physiological regulatory activities. In addition, the marine bioactive peptides may be used as ingredients in food or nutritional supplements with the function of treating or alleviating chronic diseases. This review presents an update of marine bioactive peptides with the highlights on the novel producing technologies, the physiological effects, as well as their regulation mechanisms. Challenges and problems are also discussed in this review to provide some potential directions for future research.

Can be marine bioactive peptides (MBAs) lead the future of foodomics for human health?

Marine organisms are considered a cache of biologically active metabolites with pharmaceutical, functional, and nutraceutical properties. Among these, marine bioactive peptides (MBAs) present in diverse marine species (fish, sponges, cyanobacteria, fungi, ascidians, seaweeds, & mollusks) have acquired attention owing to their broad-spectrum health-promoting benefits. Nowadays, scientists are keener exploring marine bioactive peptides precisely due to their unique structural and biological properties. These MBAs have reported ameliorating potential against different diseases like hypertension, diabetes, obesity, HIV, cancer, oxidation, and inflammation. Furthermore, MBAs isolated from various marine organisms may also have a beneficial role in the cosmetic, nutraceutical, and food industries. Few marine peptides and their derivative are approved for commercial use, while many MBAs are in various pre-clinical and clinical trials. This review mainly focuses on the diversity of marine bioactive peptides in marine organisms and their production procedures, such as chemical and enzymatic hydrolysis. Moreover, MBAs' therapeutic and biological potential has also been critically discussed herein, along with their status in drug discovery, pre-clinical and clinical trials.

Exploiting of Secondary Raw Materials from Fish Processing Industry as a Source of Bioactive Peptide-Rich Protein Hydrolysates

Developing peptide-based drugs are very promising to address many of the lifestyle mediated diseases which are prevalent in a major portion of the global population. As an alternative to synthetic peptide-based drugs, derived peptides from natural sources have gained a greater attention in the last two decades. Aquatic organisms including plants, fish and shellfish are known as a rich reservoir of parent protein molecules which can offer novel sequences of amino acids in peptides, having unique bio-functional properties upon hydrolyzing with proteases from different sources. However, rather than exploiting fish and shellfish stocks which are already under pressure due to overexploitation, the processing discards, regarded as secondary raw material, could be a potential choice for peptide based therapeutic development strategies. In this connection, we have attempted to review the scientific reports in this area of research that deal with some of the well-established bioactive properties, such as antihypertensive, anti-oxidative, anti-coagulative, antibacterial and anticarcinogenic properties, with reference to the type of enzymes, substrate used, degree of particular bio-functionality, mechanism, and wherever possible, the active amino acid sequences in peptides. Many of the studies have been conducted on hydrolysate (crude mixture of peptides) enriched with low molecular bioactive peptides. In vitro and in vivo experiments on the potency of bioactive peptides to modulate the human physiological functions beneficially have demonstrated that these peptides can be used in the prevention and treatment of non-communicable lifestyle mediated diseases. The information synthesized under this review could serve as a point of reference to drive further research on and development of functionally active therapeutic natural peptides. Availability of such scientific information is expected to open up new zones of investigation for adding value to underutilized secondary raw materials, which in turn paves the way for sustainability in fish processing. However, there are significant challenges ahead in exploring the fish waste as a source of bioactive peptides, as it demands more studies on mechanisms and structure–function relationship understanding as well as clearance from regulatory and statutory bodies before reaching the end user in the form of supplement or therapeutics.

Fish Waste: From Problem to Valuable Resource

Following the growth of the global population and the subsequent rapid increase in urbanization and industrialization, the fisheries and aquaculture production has seen a massive increase driven mainly by the development of fishing technologies. Accordingly, a remarkable increase in the amount of fish waste has been produced around the world; it has been estimated that about two-thirds of the total amount of fish is discarded as waste, creating huge economic and environmental concerns. For this reason, the disposal and recycling of these wastes has become a key issue to be resolved. With the growing attention of the circular economy, the exploitation of underused or discarded marine material can represent a sustainable strategy for the realization of a circular bioeconomy, with the production of materials with high added value. In this study, we underline the enormous role that fish waste can have in the socio-economic sector. This review presents the different compounds with high commercial value obtained by fish byproducts, including collagen, enzymes, and bioactive peptides, and lists their possible applications in different fields.

Copper-chelating peptide from salmon by-product proteolysate

The aims of this study included evaluation of copper-binding capacity (CBC) and amino acid composition of salmon by-product proteolysate and its peptide fractions, optimization of hydrolysis condition, and identification of copper-binding peptides from the proteolysate. The result was that under the ideal hydrolysis (Neutrase, temperature of 45 °C, pH 7, enzyme:substrate (E:S) proportion of 72.24 U/g protein and hydrolysis time of 8.02 h), the proteolysate had the indispensable amino acid content at approximately 38.7% and also displayed the maximal CBC of 15163.6 µg Cu2+/g protein. Besides, four peptide fractions of 10–30 kDa, 3–10 kDa, 1–3 kDa, and <1 kDa were recovered using ultrafiltration, among which the <1 kDa fraction had the highest CBC of 10852.00 ± 895.06 µgCu2+/g protein. A copper-binding peptide, Phe-Ile-Asp-Asp-Asp-Ala-Phe-Ile-Arg (1110 Da), was identified from this fraction using tandem mass spectrometry (MS/MS). As a whole, the proteolysate/peptides could be used for copper enhancement that could shield human body from copper inadequacy disorders.

Production, Characterization, and Bioactivity of Fish Protein Hydrolysates from Aquaculture Turbot (Scophthalmus maximus) Wastes

The valorization of wastes generated in the processing of farmed fish is currently an issue of extreme relevance for the industry, aiming to accomplish the objectives of circular bioeconomy. In the present report, turbot (Scophthalmus maximus) by-products were subjected to Alcalase hydrolysis under the optimal conditions initially defined by response surface methodology. All the fish protein hydrolysates (FPHs) showed a high yield of digestion (>83%), very remarkable degrees of hydrolysis (30–37%), high content of soluble protein (>62 g/L), an excellent profile of amino acids, and almost total in vitro digestibility (higher than 92%). Antioxidant and antihypertensive activities were analyzed in all cases, viscera hydrolysates being the most active. The range of average molecular weights (Mw) of turbot hydrolysates varied from 1200 to 1669 Da, and peptide size distribution showed that the hydrolysate of viscera had the highest content of peptides above 1000 Da and below 200 Da.

Aquaculture and its by-products as a source of nutrients and bioactive compounds

Underutilized marine resources (e.g., algae, fish, and shellfish processing by-products), as sustainable alternatives to livestock protein and interesting sources of bioactive compounds, have attracted the attention of the researchers. Aquatic products processing industries are growing globally and producing huge amounts of by-products that often discarded as waste. However, recent studies pointed out that marine waste contains several valuable components including high-quality proteins, lipids, minerals, vitamins, enzymes, and bioactive compounds that can be used against cancer and some cardiovascular disorders. Besides, previously conducted studies on algae have shown the presence of some unique biologically active compounds and valuable proteins. Hence, this chapter points out recent advances in this area of research and discusses the importance of aquaculture and fish processing by-products as alternative sources of proteins and bioactive compounds.

Fish and fish side streams are valuable sources of high-value components

The current practice of fish processing generates increasing quantities of side streams and waste, such as skin, heads, frames, viscera, and fillet cut offs. These may account for up to 70% of the fish used in industrial processing. Low-value fish catches, and under-utilized fish species comprise another source of side streams. These side streams have been discarded in the environment leading to environmental problems or they have ended up as low commercial value products, such as feed for fur animals and aquaculture. However, several studies have shown that fish side streams contain valuable bioactive ingredients and fractions, such as fish oils, proteins and peptides, collagen, gelatin, enzymes, chitin, and minerals. These compounds and fractions may provide the opportunity to develop novel applications in health promoting foods, special feeds, nutraceuticals, pharmaceuticals, and cosmetic products. Better utilization of side streams and low-value fish would simultaneously improve both the environmental and ecological sustainability of production. This review summarizes the current knowledge on fish and fish side streams as sources of high-value components such as peptides with antimicrobial, antioxidative, antihypertensive, and antihyperglycemic properties, proteins such as fish collagen and gelatin, fish enzymes, fish oils and fatty acids, polysaccharides like glucosaminoglycans, chitin and chitosan, vitamin D, and minerals. Production technologies for recovering the high-value fractions and potential product applications are discussed. Furthermore, safety aspects related to the raw material, technologies, and fractions are considered.

Facile preparation of a Ca(ii) carboxymethyl cellulose complex with enhanced calcium bioavailability for treatment of osteoporosis

At present, though calcium (Ca) reagents with high calcium contents are widely synthesized, their wide application is limited due to their low absorption rates and poor bioavailability. Here we use a carboxymethyl cellulose (CMC) derivative with high water solubility and biocompatibility as a ligand to bind Ca2+. The resulting CaCMC complex exhibits remarkable solubility and absorbability under both basic and acidic conditions as well as in stomach mimicking and the gastrointestinal tract. Importantly, this Ca reagent shows high in vivo calcium bioavailability. Data from osteoporosis mouse models show that the CaCMC complex is superior to calcium carbonate in the treatment of osteoporosis. Therefore, the resulting CaCMC complex is used as a new, highly effective and desirable Ca supplement for daily life and clinical applications.

Optimization of antioxidative peptides from mackerel (Pneumatophorus japonicus) viscera

Mackerel (Pneumatophorus japonicus) viscera contain large amount of protein. We used five proteases to hydrolyze the viscera, and the hydrolysate treated by neutrase exhibited the highest nitrogen recovery (NR). Then we optimized the preparation conditions for mackerel viscera hydrolysate (MVH) by response surface methodology and investigated the antioxidant activity of MVH. The optimal conditions were as follows: enzyme concentration of 1,762.87 U/g, pH of 6.76, temperature of 43.75 °C, extraction time of 6.0 h and water/material ratio of 20.37 (v/w), and the maximum NR was 37.84%. Furthermore, the molecular weight distribution of MVH was almost below 3,000 Da determined by TSK G2000 SWXL gel filtration chromatography, and the MVH exhibited good antioxidant activities in various in vitro assays, including DPPH radical, hydroxyl radical and superoxide anion scavenging activities, reducing power and similar effectivelness as butylated hydroxytoluene and Vitamin E to inhibit lipid peroxidation. The results suggested that MVH could be used as a potential source of antioxidant peptide in food industries.

Microencapsulation of Phosphorylated Human-Like Collagen-Calcium Chelates for Controlled Delivery and Improved Bioavailability

The bioavailability of Phosphorylated Human-like Collagen-calcium chelates (PHLC-Ca) as calcium supplement is influenced by the extremely low pH and proteolytic enzymes in the gastrointestinal tract. This study addresses these issues by microencapsulation technology using alginate (ALG) and chitosan (CS) as wall materials. The different ratio of ALG to PHLC-Ca on microcapsules encapsulation efficiency (EE) and loading capacity (LC) was evaluated and 1:1/2 was selected as the optimal proportion. The microcapsules were micron-sized and spherical in shape. PHLC-Ca was successfully entrapped into the matrix of ALG through forming intermolecular hydrogen bonding or other interactions. The confocal laser scanning microscopy (CLSM) indicated that CS was coated on ALG microspheres. The MTT assay exhibited that CS/ALG-(PHLC-Ca) microcapsules extracts were safe to L929. The animal experiment showed that CS/ALG-(PHLC-Ca) microcapsules was superior to treating osteoporosis than PHLC-Ca. These results illustrated that the bioavailability of PHLC-Ca was improved by microencapsulated.

Characterization, Preparation, and Purification of Marine Bioactive Peptides

Marine bioactive peptides, as a source of unique bioactive compounds, are the focus of current research. They exert various biological roles, some of the most crucial of which are antioxidant activity, antimicrobial activity, anticancer activity, antihypertensive activity, anti-inflammatory activity, and so forth, and specific characteristics of the bioactivities are described. This review also describes various manufacturing techniques for marine bioactive peptides using organic synthesis, microwave assisted extraction, chemical hydrolysis, and enzymes hydrolysis. Finally, purification of marine bioactive peptides is described, including gel or size exclusion chromatography, ion-exchange column chromatography, and reversed-phase high-performance liquid chromatography, which are aimed at finding a fast, simple, and effective method to obtain the target peptides.

Isolation of a novel calcium-binding peptide from wheat germ protein hydrolysates and the prediction for its mechanism of combination

To isolate a novel peptide with specific calcium-binding capacity, wheat germ protein was hydrolyzed. The hydrolysates were purified using ultrafiltration, anion-exchange chromatography, gel filtration chromatography, and reversed-phase high performance liquid chromatography. The amino acid sequence of the purified peptide was determined and confirmed to be FVDVT (Phe-Val-Asp-Val-Thr). The calcium-binding capacity of FVDVT reached 89.94±0.75%, increased by 86.37% compared to the hydrolysates. The chelating mechanism between FVDVT and calcium was further investigated by Ultraviolet-Visible absorption spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and ¹H nuclear magnetic resonances spectroscopy. The results indicated that the oxygen atoms of the carboxy group and the nitrogen atoms of the amido group provided major binding sites. In addition, aspartic acid and threonine show considerable capacity for incorporating with calcium by donating electron pairs. This study provides a feasible approach to isolate calcium-binding peptides and to clarify the possible binding mechanism of calcium and peptide.

A Specific Peptide with Calcium-Binding Capacity from Defatted Schizochytrium sp. Protein Hydrolysates and the Molecular Properties

Marine microorganisms have been proposed as a new kind of protein source. Efforts are needed in order to transform the protein-rich biological wastes left after lipid extraction into value-added bio-products. Thus, the utilization of protein recovered from defatted Schizochytrium sp. by-products presents an opportunity. A specific peptide Tyr-Leu (YL) with calcium-binding capacity was purified from defatted Schizochytrium sp. protein hydrolysates through gel filtration chromatography and RP-HPLC. The calcium-binding activity of YL reached 126.34 ± 3.40 μg/mg. The calcium-binding mechanism was investigated through ultraviolet, fluorescence and infrared spectroscopy. The results showed that calcium ions could form dative bonds with carboxyl oxygen atoms and amino nitrogen atoms as well as the nitrogen and oxygen atoms of amide bonds. YL-Ca exhibited excellent thermal stability and solubility, which was beneficial for its absorption and transport in the basic intestinal tract of the human body. Moreover, the cellular uptake of calcium in Caco-2 cells showed that YL-Ca could enhance calcium uptake efficiency and protect calcium ions against precipitation caused by dietary inhibitors such as tannic acid, oxalate, phytate and metal ions. The findings indicate that the by-product of Schizochytrium sp. is a promising source for making peptide-calcium bio-products as algae-based functional supplements for human beings.

Fish viscera protein hydrolysates: Production, potential applications and functional and bioactive properties

The aquaculture and fishery chain is an important part of the economy of many countries around the world; in recent years it has experienced significant growth that generates more and more quantities of waste, which are mostly discarded, impacting the environment, despite having a useful chemical composition in various industrial sectors. This article presents a review of the agroindustrial potential of fish wastes, especially viscera, as a source for obtaining native protein and hydrolysates, explaining their production process, chemical composition and functional and bioactive properties that are important to the agricultural, cosmetic, pharmaceutical, food and nutraceutical industry.

Effect of calcium-binding peptide from Pacific cod (Gadus macrocephalus) bone on calcium bioavailability in rats

Bone collagen peptide with high affinity to Ca was extracted from Pacific cod (Gadus macrocephalus) bone. FTIR spectra of calcium-binding bone collagen peptide showed that band at 3381cm^-1 shifted to 3361cm^-1, 1455cm^-1 moved to 1411cm^-1, and amide II became deeper valley, compared with that of bone collagen peptide. This peptide was sequenced by Q-TOF-MS and sequences of Gly-Pro-Glu-Gly, Gly-Glu-Lys, Gly-Pro-Leu-Gly and Gly-Leu-Pro-Gly appeared repeatedly in some peptides. From SEM, after chelated with calcium, the loose and porous structure turned into granular structure. From the animal experiment, Ca apparent absorption rate, Ca retention rate and femur Ca content of calcium-binding bone collagen peptide group were significantly higher than those of model and CaCO₃ groups (P<0.05), while serum ALP was significantly lower than model group (P<0.05) and similar to control group. The results suggested that calcium-binding bone collagen peptide could improve bioavailability of Ca and thus prevented Ca deficiency.

Identification of peptides, metal binding and lipid peroxidation activities of HPLC fractions of hydrolyzed oat bran proteins

The aim of this study was to evaluate metal binding and antioxidant activities of hydrolyzed oat bran proteins followed by the determination of peptide sequences. Protamex oat bran protein hydrolysates (OBPH) were separated by reverse-phase HPLC into eight peptide fractions (F1-F8) and their abilities to either chelate metals (Fe²⁺, Ca²⁺) or prevent the oxidation of lipids were investigated. In the Fe²⁺ chelation assay, OBPH had significantly (p < 0.05) higher activity (39.7 %) than the best performed fraction F7 (22.8 %). The second most active was F5 with 12.1 % chelating activity and this was higher than the activity of the tripeptide glutathione (5.8 %) used as control. The two most Fe²⁺ chelating fractions (F5, F7) however had weak calcium binding (0.6-1.0 %) properties at peptide concentration ranging from 0.2 to 1.0 mg/mL. In the lipid peroxidation assay, OBPH and all HPLC fractions prevented the oxidation of linoleic acid. More than 60 peptides mainly derived from globulin and avenin proteins were identified using tandem mass spectrometry.

Preparation and Evaluation of the Chelating Nanocomposite Fabricated with Marine Algae Schizochytrium sp. Protein Hydrolysate and Calcium

Marine algae have been becoming a popular research topic because of their biological implication. The algae peptide-based metal-chelating complex was investigated in this study. Schizochytrium sp. protein hydrolysate (SPH) possessing high Ca-binding capacity was prepared through stepwise enzymatic hydrolysis to a degree of hydrolysis of 22.46%. The nanocomposites of SPH chelated with calcium ions were fabricated in aqueous solution at pH 6 and 30 °C for 20 min, with the ratio of SPH to calcium 3:1 (w/w). The size distribution showed that the nanocomposite had compact structure with a radius of 68.16 ± 0.50 nm. SPH was rich in acidic amino acids, accounting for 33.55%, which are liable to bind with calcium ions. The molecular mass distribution demonstrated that the molecular mass of SPH was principally concentrated at 180-2000 Da. UV scanning spectroscopy and Fourier transform infrared spectroscopy suggested that the primary sites of calcium-binding corresponded to the carboxyl groups, carbonyl groups, and amino groups of SPH. The results of fluorescent spectroscopy, size distribution, atomic force microscope, and (1)H nuclear magnetic resonance spectroscopy suggested that calcium ions chelated with SPH would cause intramolecular and intermolecular folding and aggregating. The SPH-calcium chelate exerted remarkable stability and absorbability under either acidic or basic conditions, which was in favor of calcium absorption in the gastrointestinal tracts of humans. The investigation suggests that SPH-calcium chelate has the potential prospect to be utilized as a nutraceutical supplement to improve bone health in the human body.

Novel peptide with a specific calcium-binding capacity from whey protein hydrolysate and the possible chelating mode

A novel peptide with a specific calcium-binding capacity was isolated from whey protein hydrolysates. The isolation procedures included diethylaminoethyl (DEAE) anion-exchange chromatography, Sephadex G-25 gel filtration, and reversed-phase high-performance liquid chromatography (HPLC). A peptide with a molecular mass of 237.99 Da was identified by liquid chromatography-electrospray ionization/mass spectrometry (LC-ESI/MS), and its amino acid sequence was confirmed to be Gly-Tyr. The calcium-binding capacity of Gly-Tyr reached 75.38 μg/mg, increasing by 122% when compared to the hydrolysate complex. The chelating interaction mode between the Gly-Tyr and calcium ion was investigated, indicating that the major binding sites included the oxygen atom of the carbonyl group and nitrogen of the amino or imino group. The folding and structural modification of the peptide arose along with the addition of the calcium ion. The profile of (1)H nuclear magnetic resonance (NMR) spectroscopy demonstrated that the electron cloud density around the hydrogen nucleus in the peptide changed was caused by the calcium ion. The results of ζ potential showed that the Gly-Tyr-Ca chelate was a neutral molecule in which the calcium ion was surrounded by the specific binding sites of the peptide. Moreover, thermogravimetry-differential scanning calorimetry (TG-DSC) and calcium-releasing assay revealed that the Gly-Tyr-Ca chelate exerted excellent thermal stability and solubility in both acidic and basic conditions, which were beneficial to calcium absorption in the gastrointestinal tract of the human body and, therefore, improved its bioavailability. These findings further the progress in the research of whey protein, suggesting the potential in making peptide-calcium chelate as a dietary supplement.

Calcium-binding capacity of wheat germ protein hydrolysate and characterization of Peptide-calcium complex

This study investigates the ability of various wheat germ protein hydrolysates (WGPHs) to bind calcium and characterizes the peptide-calcium complexes. We demonstrate that the amount of Ca bound depended greatly on the type of enzyme, degree of hydrolysis (DH), amino acid composition, and molecular mass distribution of different hydrolysates. The maximum level of Ca bound (67.5 mg·g(-1)) occurred when Alcalase was used to hydrolyze wheat germ protein at a DH of 21.5%. Peptide fragments exhibiting high calcium-binding capacity had molecular mass <2000 Da. The calcium-binding peptides mainly consisted of Glu, Arg, Asp, and Gly, and the level of Ca bound was related to the hydrophobic amino acid content in WGPHs. UV-visible and Fourier transform infrared spectra demonstrate that amino nitrogen atoms and oxygen atoms on the carboxyl group were involved in complexation. Therefore, wheat germ protein is a promising protein source for the production of calcium-binding peptides and could be utilized as a bioactive ingredient for nutraceutical food production.

Formation and characterization of iron-binding phosphorylated human-like collagen as a potential iron supplement

Iron incorporated into food can induce precipitation and unwanted interaction with other components in food. Iron-binding proteins represent a possibility to avoid these problems and other side effects, as the iron is protected. However, there are several technical problems associated with protein-iron complex formation. In this paper, the iron-binding phosphorylated human-like collagen (Fe-G6P-HLC) was prepared under physiological conditions through phosphorylated modification. One molecule of Fe-G6P-HLC possesses about 24 atoms of Fe. Spectroscopy analysis, differential scanning calorimetry (DSC) and equilibrium dialysis techniques were employed to investigate the characteristics of the Fe-G6P-HLC. The binding sites (nb) and apparent association constant (Kapp) between iron and phosphorylated HLC were measured at nb=23.7 and log Kapp=4.57, respectively. The amount of iron (Fe(2+) sulfate) binding to phosphorylated HLC was found to be a function of pH and phosphate content. In addition, the solubility and thermal stability of HLC were not significantly affected. The results should facilitate the utilization of HLC as a bioactive iron supplement in the food and medical industry and provide an important theoretical evidence for the application of HLC chelates.