The Bioactivities In Vitro And The Stability Of Milk-derived Immunomodulating Peptides

Immunomodulating peptides have been defined as specific proteinfragments that have a positive impact on body functions which canimprove and modulate the immune systems. With the fast developmentof the science and technology, more and more immunomodulatingpeptides were discovered and applied to the food and medicine industries.It has been a heated research topic in the world.My experiment was divided into three parts: the research on itsimmunomodulating effects, the other bioactivity of angiotensinconverting enzyme (ACE) inhibitory and its stability.The experiment started from two main immune cells that arelymphocytes and macrophages to study on the mechanism. For thelymphocytes, proliferation, cell cycle and the secretion of IL-4and IFN-γwere tested. The results showed QEPVL had a significant effect onlymphocyte proliferation and the secretion of IL-4and IFN-γ in vitro. Forthe macrophages, proliferation, neutral red phagocytosis and inducednitric oxide secretion were tested. However, the results were not assignificant as those of the lymphocyte. According to these results, weinduce that QEPVL plays its role of immunomodulating by influencinglymphocytes.To learn more about the relationship between the other bioactivitiesand immunomodulating effect, the bioactivity of angiotensin convertingenzyme (ACE) inhibitory was studied. By RP-HPLC, QEPVL was found tohave an effect on inhibiting the angiotensin converting enzyme and its IC50 was701.3μM and further study showed that the QEPVL was a potentcompetitive inhibitor of ACE with a Ki of6.05mM. We infer that QEVPLinhibits the degradation of kallidin by competing inhibiting ACE to play apart in immunomodulating indirectly.The influence of the enviroment of outside and inner human bodywas also studied.QEPVL was exposed to different pH, tempertures, timesas well as diverse enzymes to simulate the gastrointestinal digestion. Theresults showed that QEPVL was quite stable to different pH, temperturesand times. In the gastrointestinal digestion, QEPVL was enzymolyed toQEPV analysised by UPLC-Q-TOF-MS while its immunomodulating abilitywas barely affected. This meant that QEPVL was almost resistant todigestion by proteases of the gastrointestinal tract.The mechanism of immunomodulating activity and its stability weredeeply studied in this project. The results provide an appearing possibliltyfor its further study in vivo and industrialization.