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Antarctic krill (Euphausia superba) is a nutrient-rich marine resource. Although several terrestrial proteases have been used to prepare Antarctic krill peptides (AKPs), there has been no report on the preparation of AKPs using a marine protease. Here, marine bacterial protease A69 was used to prepare AKPs with multi-bioactivities. Through optimizing hydrolysis parameters, we established a process for AKPs preparation by hydrolyzing Antarctic krill powder with A69. In the prepared AKPs, peptides less than 3000 Da and 1000 Da accounted for 99.23% and 88.37%, respectively. The scavenging ratios of the AKPs to ABTS+, DPPH· and ·OH reached 93.23 ± 0.09%, 99.90 ± 0.15%, and 93.90 ± 0.47%, respectively. The AKPs also had high angiotensin-converting enzyme (ACE)-inhibitory activity, with an IC50 of 0.22 ± 0.04 mg/mL. At 40 mg/mL, the AKPs inhibited α-glucosidase and dipeptidyl peptidase IV (DPP-IV) activities by 7.18% and 13.62%, respectively, and displayed antibacterial activity to Escherichia coli. Moreover, 14 antioxidant peptides, 24 ACE-inhibitory peptides, 2 α-glucosidase-inhibitory peptides, and 10 DPP-Ⅳ-inhibitory peptides were identified from the AKPs. These results demonstrate that the prepared AKPs contain diverse bioactive peptides and have multi-bioactivities. This study indicates that marine bacterial protease A69 has promising application potential in preparing AKPs with multi-bioactivities.

In the present study, whey protein was enzymatically hydrolyzed using an ultrahigh‐pressure synergistic enzymolysis method. The antioxidant activities and DPP‐IV inhibitory activities of the enzymatic hydrolysates were measured. Three‐layer isolation and purification were conducted on the enzymatic hydrolysates with antioxidant activity and DPP‐IV inhibitory activity by gel filtration chromatography and RP‐HPLC. The amino acid sequences were determined by LC‐MS/MS. The identified amino acid sequences were then synthesized, and their antioxidants and DPP‐IV inhibitory activities were determined. The results showed that 3 of the 14 polypeptides of N3‐8 exhibited high antioxidant activity. Among them, peptide DDQNPHSSN had both high antioxidant activity and DPP‐IV inhibitory activity. When the concentration was 1 mg/mL, then the ABTS radical scavenging rate, DPPH radical scavenging rate and reducing power were prominent, reaching 91.42%, 88.76%, and 0.637%, respectively, and DPP‐IV inhibitory activity reached 66.28%. Whey protease hydrolysates are expected to be commercially developed as functional peptides. Whey protein was enzymatically hydrolyzed using an ultrahigh‐pressure synergistic enzymolysis method. The identified amino acid sequences were then synthesized, and their antioxidants and DPP‐IV inhibitory activities were determined. Whey protease hydrolysates could potentially be expected to be successfully commercially developed as functional peptides in the future.

In this study, some biological activities including antioxidant activity (DPPH radical scavenging activity, ABTS radical scavenging activity, and CUPRAC assay), DPP-IV enzyme inhibitory activity, and α-glucosidase enzyme inhibitory activity of peptides released from in vitro gastrointestinal digested casein and the whey proteins of camel and donkey milk were evaluated. While the highest antioxidant activity was determined to be in the digested camel casein fraction using the ABTS and CUPRAC methods, the digested donkey casein fraction was determined to have the highest radical scavenging activity using the DPPH method. The highest DPP-IV inhibitory activity was detected in digested camel and donkey milk casein fractions. Digested whey fractions of camel and donkey milk had a lower DPP-IV inhibitory activity compared to the digested casein fractions. However, digested whey fractions of camel and donkey milk did not show α-glucosidase inhibitory activity, and digested donkey casein fraction showed the highest α-glucosidase inhibitory activity with a 12.5 µg/mL IC50 value. It was concluded that peptides released from digested casein fraction of camel and donkey milk have potent antioxidant and particularly antidiabetic properties.

In this study, we studied the bioactive peptides produced by thermolysin hydrolysis of a water-soluble protein (WSP) from the red alga Gracilariopsis chorda, whose major components are phycobiliproteins and Ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCo). The results showed that WSP hydrolysate exhibited significantly higher ACE inhibitory activity (92% inhibition) compared to DPP-IV inhibitory activity and DPPH scavenging activity. The phycobiliproteins and RuBisCo of G. chorda contain a high proportion of hydrophobic (31.0–46.5%) and aromatic (5.1–46.5%) amino acid residues, which was considered suitable for the formation of peptides with strong ACE inhibitory activity. Therefore, we searched for peptides with strong ACE inhibitory activity and identified two novel peptides (IDHY and LVVER). Then, their interaction with human ACE was evaluated by molecular docking, and IDHY was found to be a promising inhibitor. In silico analysis was then performed on the structural factors affecting ACE inhibitory peptide release, using the predicted 3D structures of phycobiliproteins and RuBisCo. The results showed that most of the ACE inhibitory peptides are located in the highly solvent accessible α-helix. Therefore, it was suggested that G. chorda is a good source of bioactive peptides, especially ACE-inhibitory peptides.

Dipeptidyl peptidase-IV (DPP-IV) is a key target for the treatment of type 2 diabetes mellitus. It is possible that peptides that precisely regulate DPP-IV could be released from coix seed prolamins (CSP), but whether this happens has not yet been investigated. We performed the in silico digestion of CSP and predicted the bioactivity, absorption, transport, toxicity, and allergenicity of the resulting peptides. The simulation predicted that 47 non-toxic bioactive peptides would be released. After screening these, we found that 64.58% of them could possess DPP-IV inhibitory activity. The effect of thermal processing on the amino acid composition and structural properties of CSP was determined, and the DPP-IV inhibitory activity of its digestion-derived peptides was also assessed. The results showed that processing could change the flavour of coix seed and the supply of amino acids. After processing, the spatial conformation of CSP changed from ordered to disordered, and the peptide content and the DPP-IV inhibitory activity of its digestion products significantly increased by 19.89–30.91% and 36.84–42.02%, respectively. These results support the hypothesis that processing can change the protein structure and increase the probability that bioactive peptides will be released. They also have important implications for the development of bioactive peptides and the intensive processing of coix seeds.

After being treated with protease K, peptides extracted from donkey blood were separated, identified, and characterized. The results showed that Sephadex G-25 medium purified with MW < 3 kDa had the highest dipeptidyl peptidase IV (DPP-IV) inhibition capacity. Three-hundred-and-thirty-four peptides were identified with UPLC–MS/MS. Peptide Ranker and molecular docking analysis were used to screen active peptides, and 16 peptides were finalized out of the 334. The results showed that the lowest binding energy between P7(YPWTQ) and DPP-IV was −9.1, and the second-lowest binding energy between P1(VDPENFRLL) and DPP-IV was −8.7. The active peptides(MW < 3 kDa) could cause a reduction in the fasting blood glucose levels of type 2 diabetic mice, improve glucose tolerance, and facilitate healing of the damaged structure of diabetic murine liver and pancreas. Meanwhile, the peptides were found to ameliorate the diabetic murine intestinal micro-ecological environment to a certain extent.

One of the challenges related to food and agriculture industries is the production of waste and by-products. In this study, red pomegranate seeds (PS) was selected as a by-product (from oil extraction) for the production of bioactive hydrolysate (with Alcalase, pancreatin, trypsin and pepsin). The composition of essential (~ 23.3%), hydrophobic (~ 32.9%), antioxidant (~ 13.9%) amino acids, and PER index (~ 2.1) especially in hydrolysates by alcalase (H-Al) indicated the nutritional value, antioxidant activity and high digestibility of hydrolysate. Secondary structures and amide regions (I, II and III) were identified in PS-protein. Enzymolysis led to the improvement of solubility, emulsification and foaming capacity of PS-protein, especially in acidic conditions. The water and oil holding capacity were also affected by the type of proteases. The most biological activities (DPPH, ABTS, OH, NO radicals scavenging, reducing power, total antioxidant and metal-ions chelating activities), also, Angiotensin I-converting enzyme (ACE) (50.1%) and Dipeptidyl peptidase-4 (DPP-IV) (61.2%) inhibition were achieved through hydrolysis using Alcalase and pancreatin. While, the highest antibacterial effect ( E. coli and S. aureus ) was obtained after hydrolysis with Alcalase. PS- hydrolysate can be considered as a natural nutritious, functional, antioxidant, preservative, blood pressure lowering and antidiabetic compounds in food formulations and dietary supplements.

The fast development of bioinformatics and various established databases of bioactive peptides provide time-saving and efficient method for identifying bioactive peptides from various proteins. The yak bone collagen is rich in nutrition and have various potential bioactivities, but the study on yak bone collagen as a precursor of antidiabetic peptide has not been reported. In this study, yak bone collagen was first evaluated as a precursor to generate dipeptidyl peptidase-IV (DPP-IV) inhibitory peptides by in silico analysis. After multi-cycles of screening, three peptides (GHR, GIR and MGPR) were screened out and synthesized to evaluate their inhibitory activities in vitro. Among the three peptides, MGPR had the best inhibitory effect on DPP-IV with IC50 of 0.490 ± 0.012 mM. Further cell test verified that MGPR could ameliorate glucosamine-induced glucose uptake reduction in HepG2 cells. These results suggested that yak bone collagen could be applied as a good precursor for antidiabetic peptides. This study would further broaden the application of yak bone collagen in the fields of the food and pharmaceuticals industry.

The industrial processing of Argentine shortfin squid to obtain rings generates a significant amount of protein-rich waste, including the skin, which is rich in collagen and attached myofibrillar proteins. This waste is generally discarded. In this study, skin was used as a source of proteins that were hydrolysed using Trypsin, Esperase® or Alcalase®, which released peptides with antioxidant potential and, in particular, antihypertensive (ACE inhibition), hypoglycemic (DPP-IV inhibition) and/or nootropic (PEP inhibition) potential. Among the three enzymes tested, Esperase® and Alcalase produced hydrolysates with potent ACE-, DPP-IV- and PEP-inhibiting properties. These hydrolysates underwent chromatography fractionation, and the composition of the most bioactive fractions was analysed using HPLC-MS-MS. The fractions with the highest bioactivity exhibited very low IC50 values (16 and 66 µg/mL for ACE inhibition, 97 µg/mL for DPP-IV inhibition and 55 µg/mL for PEP inhibition) and were mainly derived from the hydrolysate obtained using Esperase®. The presence of Leu at the C-terminal appeared to be crucial for the ACE inhibitory activity of these fractions. The DPP-IV inhibitory activity of peptides seemed to be determined by the presence of Pro or Ala in the second position from the N-terminus, and Gly and/or Pro in the last C-terminal positions. Similarly, the presence of Pro in the peptides present in the best PEP inhibitory fraction seemed to be important in the inhibitory effect. These results demonstrate that the skin of the Argentine shortfin squid is a valuable source of bioactive peptides, suitable for incorporation into human nutrition as nutraceuticals and food supplements.