Yan Jing

In this study, corn protein hydrolysates (CPT) were prepared via enzymatic hydrolysis using Alcalase and Protamex, and then fractionated by ultrafiltration into three molecular weight components: >5 kDa (CPT1), 3–5 kDa (CPT2), and 50 values for ABTS radical scavenging and hydroxyl radical scavenging of 0.042 ± 0.003 mg/mL and 0.807 ± 0.019 mg/mL, respectively. Finally, 205 glutamine peptides were further identified from CPT3, and their structural characterization revealed that the identified peptides were rich in hydrophobic amino acids and had a high affinity for membrane proteins, which could serve as potential ligands for regulating intestinal barrier dysfunction. In summary, CPT3 possesses excellent functional properties and antioxidant activity, indicating its potential for development and application in functional and health foods.

Background: Glutamine peptides refer to a series of peptides containing glutamine, and the activity of glutamine peptides is characterized by the content of non-nitrogen terminal glutamine in the peptide. It has been found that glutamine peptides are a stable substitute for glutamine monomer, and they are increasingly studied in nutrition and physiology due to their functional properties. Methods: An extensive search of the literature was conducted in the PubMed, Web of Science, Scopus, and Google Scholar databases up to December 2024. Inclusion criteria focused on the role of glutamine peptides in intestinal health, and the included literature was screened and summarized. Results: This study systematically reviews the current status of research on the preparation, analysis, applications of glutamine peptides and their role in intestinal barrier protection. Furthermore, the challenges faced by the current research and the development direction in the future are discussed. Conclusions: Glutamine peptides can play a role in protecting the intestinal barrier by regulating tight junctions, mucin, inflammatory response, and intestinal flora. In addition, further and intensive investigations are urgently required to address the current challenges pertaining to the structure–activity relationships of glutamine peptides and their transport and absorption mechanism in the gut. This review contributes to a better understanding of the mechanism of glutamine peptides to protect intestinal barrier function and also provides a reference for the development of functional foods with protective effects of intestinal barrier function.

A novel fibrinolytic enzyme was produced by the liquid fermentation of Coprinus comatus. The enzyme was purified from the culture supernatant by hydrophobic interactions, gel filtration, and ion exchange chromatographies. It was purified by 241.02-fold, with a specific activity of 3619 U/mg and a final yield of 10.02%. SDS-PAGE analysis confirmed the purity of the enzyme, showing a single band with a molecular weight of 19.5 kDa. The first nine amino acids of the N-terminal of the purified enzyme were A-T-Y-T-G-G-S-Q-T. The enzyme exhibited optimal activity at a temperature of 42 °C and pH 7.6. Its activity was significantly improved by Zn²⁺, K⁺, Ca²⁺, Mn²⁺, and Mg²⁺ while being inhibited by Fe²⁺, Fe³⁺, Al²⁺, and Ba²⁺. The activity of the enzyme was completely inhibited by ethylenediamine tetraacetic acid (EDTA), and it was also dose-dependently inhibited by phenylmethylsulfonyl fluoride (PMSF) and soy trypsin inhibitor (SBTI). However, inhibitors such as N-α-tosyl-L-phenylalanine chloromethyl ketone (TPCK), aprotinin, and pepstatin did not significantly affect its activity, suggesting that the enzyme was a serine-like metalloproteinase. The enzyme acted as both a plasmin-like fibrinolytic enzyme and a plasminogen activator, and it also exhibited the capability to hydrolyze fibrinogen and fibrin. In vitro, it demonstrated the ability to dissolve blood clots and exhibit anticoagulant properties. Furthermore, it was found that the enzyme prolonged activated partial thromboplastin time (APTT), prothrombin time (PT), and thrombin time (TT), and reduced the levels of fibrinogen (FIB) and prothrombin activity (PA). Based on these studies, the enzyme has great potential to be developed as a natural agent for the prevention and treatment of thrombotic diseases.

Ulcerative colitis is a typical chronic inflammatory disease of the gastrointestinal tract, which has become a serious hazard to human health. The purpose of the present study was to evaluate the antagonistic effect of corn protein hydrolysate with glutamine-rich peptides on ulcerative colitis. The sequential hydrolysis of corn gluten meal by Alcalase and Protamex was conducted to prepare the hydrolysate, and then the mouse ulcerative colitis model induced by dextran sulfate sodium was applied to evaluate its biological activities. The results indicated that the hydrolysate significantly improved weight loss (p < 0.05), reduced the colonic shortening and the disease activity index, diminished the infiltration of inflammatory cells in the colonic tissue, and reduced the permeability of the colonic mucosa in mice. In addition, the hydrolysate decreased the contents of pro-inflammatory factors IL-1β, IL-6, and TNF-α, increased the anti-inflammatory factor IL-10 and oxidative stress markers GSH-Px and SOD in the animal tests. Moreover, the hydrolysate also regulated the abundance and diversity of the intestinal microbiota, improved the microbiota structure, and increased the content of beneficial bacteria including Lactobacillus and Pediococcus. These results indicated that the hydrolysate might be used as an alternative natural product for the prevention of ulcerative colitis and could be further developed into a functional food.