Soybean peptide aggregates improved calcium binding capacity

Identification and characterization of a calcium-binding peptide from salmon bone for the targeted inhibition of α-amylase in digestion

α-Amylase, essential for carbohydrate digestion, relies on calcium (Ca) for its structural integrity and enzymatic activity. This study explored the inhibitory effect of salmon bone peptides on α-amylase activity through their interaction with the enzyme's Ca-binding sites. Among the various salmon bone hydrolysates, salmon bone trypsin hydrolysate (SBTH) exhibited the highest α-amylase inhibition. The peptide IEELEEELEAER (PIE), with a sequence of Ile-Glu-Glu-Leu-Glu-Glu-Glu-Glu-Leu-Glu-Ala-Glu-Arg from SBTH, was found to specifically target the Ca-binding sites in α-amylase, interacting with key residues such as Asp206, Trp203, His201, etc. Additionally, cellular experiments using 3 T3-L1 preadipocytes indicated PIE's capability to suppress adipocyte differentiation, and decreases in intracellular triglycerides, total cholesterol, and lipid accumulation. In vivo studies also showed a significant reduction in weight gain in the group treated with PIE(6.61%)compared with the control group (33.65%). These findings suggest PIE is an effective α-amylase inhibitor, showing promise for obesity treatment.

Effect of different iron ratios on interaction and thermodynamic stability of bound whey protein isolate

Whey protein isolates (WPI) are known to have mineral-binding capacity to promote iron absorption. The aim of this study was to investigate the effect of iron ratio on the conformational structure of iron-bound whey protein isolate (WPI-Fe) and its thermodynamic stability. It was shown that the iron to protein ratio affects both the iron binding capacity of WPI and the iron valence state on the surface of WPI-Fe complexes. As the iron content increases, aggregation between protein molecules occurs. In addition, WPI-Fe nanoparticles have thermodynamic stability and Fe2+ has a high affinity with WPI for spontaneous exothermic reactions. This study demonstrates that WPI-Fe complexes can be used to efficiently deliver high-quality iron source (Fe2+) for future 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.

Reply to the 'Comment on "Deciphering calcium-binding behaviors of casein phosphopeptides by experimental approaches and molecular simulation"' by D. Horne, Food Funct., 2022, , https://doi.org/D2FO00808D

The comment regarding a method we used to calculate the binding capacity of casein phosphopeptides (CPPs) with calcium. Dr. Horne stated that we overestimated the concentration of Ca²⁺. Indeed, peptides would bind with more calcium ions with the help of phosphate ions. However, in our statement, the binding capacity of CPPs with calcium we used included the binding with calcium in the presence of phosphate. In our solution, peptides sequester calcium phosphate to form soluble core-shell nanoclusters, preventing calcium phosphate precipitating. Even if the binding capacity of CPPs with calcium are overestimated as stated by Dr. Horne, these could not be a problem in deciphering calcium-binding behaviors. Phosphate was applied only in the optimizing and screening process presented in Fig. 1 and Table 1, other experiments (Fig. 2-5 in the commented article) did not include phosphate in the reaction system. Phosphate could not be a factor of these experiments.

Potential Role of Bioactive Proteins and Peptides Derived from Legumes towards Metabolic Syndrome

Legumes have been widely consumed and used to isolate bioactive compounds, mainly proteins. The aim of this study was to review the beneficial actions of different legumes proteins and peptides updating the main findings that correlate legumes consumption and the effects on non-transmissible chronic diseases, specifically metabolic syndrome. An exhaustive revision of five relevant bioactivities (antioxidant, anti-inflammatory, antihypertensive, hypocholesterolemic -all of them linked to metabolic syndrome- and antitumoral) of proteins and peptides from legumes focused on isolation and purification, enzymatic hydrolysis and in vitro gastrointestinal digestion was carried out. The promising potential of bioactive hydrolysates and peptides from pulses has been demonstrated by in vitro tests. However, only a few studies validated these biological activities using animal models. No clinical trials have been carried out yet; so further research is required to elucidate their effective health implications.

Discovery of calcium-binding peptides derived from defatted lemon basil seeds with enhanced calcium uptake in human intestinal epithelial cells, Caco-2

It is anticipated that calcium-chelating peptides may serve to enhance the absorption of calcium. This research examined defatted lemon basil seeds (DLBS) which had been treated with Alcalase under optimized parameters for the degree of hydrolysis for proteolysis, discovering that the activity for calcium-binding in a competitive condition with phosphate ion was 60.39 ± 1.545%. The purification of the hydrolysates was performed via ultrafiltration along with reversed-phase high performance liquid chromatography (RP-HPLC). Determination of the purified peptide amino acid sequence was confirmed for both peptides and reported as Ala-Phe-Asn-Arg-Ala-Lys-Ser-Lys-Ala-Leu-Asn-Glu-Asn (AFNRAKSKALNEN; Basil-1), and Tyr-Asp-Ser-Ser-Gly-Gly-Pro-Thr-Pro-Trp-Leu-Ser-Pro-Tyr (YDSSGGPTPWLSPY; Basil-2). The respective activities for calcium-binding were 38.62 ± 1.33%, and 42.19 ± 2.27%. Fluorescence spectroscopy, and fourier transform infrared spectroscopy were employed in order to assess the chelating mechanism between calcium and the peptides. It was found that the calcium ions took place through the activity of the amino nitrogen atoms and the oxygen atoms on the carboxyl group. Moreover, both of these peptides served to improve calcium transport and absorption in Caco-2 cell monolayers, depending on the concentration involved. It was revealed that the peptide-calcium complexes offered an increased calcium absorption percentage when compared to free calcium at similar concentrations. It might be concluded that the peptide within the peptide-calcium complex can promote calcium absorption through both active and passive transport pathways by increasing calcium concentration and promoting cell membrane interaction. Accordingly, DLBS protein can be considered a strong potential source of protein which can be used to produce calcium-binding peptides and might therefore play a role in the production of nutraceutical foods as a bioactive ingredient.

Changes in the secondary structures and zeta potential of soybean peptide and its calcium complexes in different solution environments

To illustrate the relationship between environment hydrophobicity and soybean peptide and its calcium complexes when they are absorbed transmembrane, different solution environments (HBS buffer, TFE hydrophobic solution and cell suspension) were used to simulate hydrophilic and hydrophobic environments. In this study, soybean peptides (10-30 kDa) with a high calcium binding capacity were prepared by enzymatic hydrolysis and ultrafiltration. The results of cell experiments showed that the peptide could transport calcium into cells for absorption. Secondary structure changes of the peptide and its calcium complexes in different solution environments showed that the secondary structure of the peptide changed during the transmembrane absorption, and the contents of α-helix and β-sheet structures increased. Besides, the β-sheet structures in the peptide-calcium complexes were further converted to an α-helix structure. This conversion may be induced by the hydrophobicity of peptide solutions. In addition, when the conformation changes, the positively charged peptides in the sample will be exposed and then interact with cells, which is beneficial for the transmembrane of peptide-calcium complexes.

Structural characterization of calcium-binding sunflower seed and peanut peptides and enhanced calcium transport by calcium complexes in Caco-2 cells

BACKGROUND

Peptide-Ca complexes can promote Ca absorption. The present study aimed to determine the transport mechanism and structural characteristics of sunflower seed and peanut peptides with high Ca binding capacity with respect to developing third-generation Ca supplements and functional food ingredients.

RESULTS

High Ca-binding fractions of 1-3 kDa sunflower seed peptide (SSP₄ ) and ≥ 10 kDa peanut peptide (PP₁ ) had higher amount of Ca transported than CaCl₂ and two hydrolyzed proteins in Caco-2 cells. SSP₄ and PP₁ were separated by Ca ion metal chelate affinity chromatography, and high Ca-binding fractions were observed for SSP₄ -P₂ and PP₁ -P₂ . The amino acid sequences of SSP₄ -P₂ and PP₁ -P₂ were characterized by high-performance liquid chromatography-electrospray ionization-time of flight mass spectrometry. Seven and eight peptides were identified from SSP₄ -P₂ and PP₁ -P₂ , respectively. These peptides had molecular weights ranging from 1500 Da to 2500 Da and a large number of characteristic amino acid sequences, such as EEEQQQ, EQ-QQQ-QQ, QQ-QQQQQ, E-EEE, EE-EEQ, RR, Q-QQ-QQQ, EE-EQ-EE-Q, QQ-QQQQ, and Q-QQQQ, where 'E' is glutamic acid and 'Q' is glutamine.

CONCLUSION

SSP₄ and PP₁ can promote Ca transport in Caco-2 cells without affecting cell permeability. The amino acid sequences of SSP₄ -P₂ and PP₁ -P₂ with high Ca-binding abilities contain characteristic sequences, such as continuous glutamic acid and glutamine, and have low molecular weights. © 2020 Society of Chemical Industry.

Three Newly Isolated Calcium-Chelating Peptides from Tilapia Bone Collagen Hydrolysate Enhance Calcium Absorption Activity in Intestinal Caco-2 Cells

In this study, we used reversed-phase high performance liquid chromatography (LC) to isolate three novel peptides with calcium-chelating capacity from tilapia bone collagen hydrolysate. Using LC-tandem mass spectrometry, we determined the amino acid sequences to be GPAGPHGPVG, FDHIVY, and YQEPVIAPKL. We then synthesized the three peptides and verified their calcium-chelating activity. Results showed that the calcium-chelating activity of GPAGPHGPVG, FDHIVY, and YQEPVIAPKL reached 18.80 ± 0.49, 35.73 ± 0.74, and 28.4 ± 0.94 mg/g, respectively. We next investigated how each peptide enhanced intestinal calcium absorption using Caco-2 cell monolayers. Compared with the control group, GPAGPHGPVG, FDHIVY, and YQEPVIAPKL potently enhanced calcium transport within 30 min by 89 ± 9, 202 ± 12, and 130 ± 7%, respectively. Results suggest that these peptides isolated from tilapia bone hydrolysate can be used as dietary supplements to increase calcium absorption.

Effect of Chlorella Pyrenoidosa Protein Hydrolysate-Calcium Chelate on Calcium Absorption Metabolism and Gut Microbiota Composition in Low-Calcium Diet-Fed Rats

In our current investigation, we evaluated the effect of Chlorella pyrenoidosa protein hydrolysate (CPPH) and Chlorella pyrenoidosa protein hydrolysate-calcium chelate (CPPH-Ca) on calcium absorption and gut microbiota composition, as well as their in vivo regulatory mechanism in SD rats fed low-calcium diets. Potent major compounds in CPPH were characterized by HPLC-MS/MS, and the calcium-binding mechanism was investigated through ultraviolet and infrared spectroscopy. Using high-throughput next-generation 16S rRNA gene sequencing, we analyzed the composition of gut microbiota in rats. Our study showed that HCPPH-Ca increased the levels of body weight gain, serum Ca, bone activity, bone mineral density (BMD) and bone mineral content (BMC), while decreased serum alkaline phosphatase (ALP) and inhibited the morphological changes of bone. HCPPH-Ca up-regulated the gene expressions of transient receptor potential cation V5 (TRPV5), TRPV6, calcium-binding protein-D9k (CaBP-D9k) and a calcium pump (plasma membrane Ca-ATPase, PMCA1b). It also improved the abundances of Firmicutes and Lactobacillus. Bifidobacterium and Sutterella were both positively correlated with calcium absorption. Collectively, these findings illustrate the potential of HCPPH-Ca as an effective calcium supplement.