Synthesis And Antioxidative Activity Of Glutamine Dipeptide

Glutamine is a conditionally essential amino acid with important physiological functions such as antioxidation and immunity enhancement.It is very important to the human body under oxidative stress conditions,but its low solubility and poor stability limit its use in the food field.At present,the enzymatic hydrolysis method is mainly used in the food field to prepare glutamine peptide,and its physiological function is studied.However,the correlation between its structural composition and physiological function is not clear.Glycyl-glutamine is a glutamine substitute,which overcomes the above shortcomings of glutamine while retaining the physiological function of glutamine.In order to further improve the antioxidant activity of glutamine peptide,the catalytic active center of natural glutathione peroxidase--selenocysteine（Sec）,was introduced to design and synthesize selenocysteine-glutamine,and its antioxidant properties studies.Glycyl-glutamine was prepared by chemical method.Through infrared characterization and thin layer analysis,the results showed that the amide bond C=O stretching vibration absorption peak at 1699.67 cm^-1,the target product was consistent with the standard product thin layer analysis,and the synthesized product was glycyl-glutamine.The selenocysteine-glutamine was prepared by chemical method.Through mass spectrometry characterization and thin layer analysis,the results showed that the actual value of selenocysteine-glutamine was consistent with the theoretical value,and the synthesized product was selenocysteine-glutamine.The glutathione peroxidase（GPX）activity,optimum temperature and p H value of glutamine dipeptide were determined by enzyme coupling method.Glycyl-glutamine did not have glutathione peroxidase activity;The glutathione peroxidase activity of selenocysteine-glutamine was 0.3985 U/μmol,which was 8 times that of selenocysteine,mainly because selenocysteine-glutamine could identify and bind of substrates which improving its GPX activity.The optimum temperature for selenocysteine-glutamine to exert GPX activity was 46.5℃,and the optimum p H was 7.12.The antioxidant activity of glutamine dipeptide was determined by four chemical methods.Glycyl-glutamine had poor DPPH radical and reducing power.Hydroxyl radical and superoxide anion scavenging ability of glycyl-glutamine were good;Selenocysteine-glutamine had good DPPH radical,hydroxyl radical,superoxide anion scavenging ability and reducing power.The protective effect of glutamine dipeptide on mitochondrial oxidative damage was studied at the subcellular level,The results showed that glutamine dipeptide could inhibit the increase of mitochondrial swelling,the increase of malondialdehyde,the increase of carbonyl,the decrease of catalase the activity,and the decrease of superoxide dismutase activity;The protective effect of selenocysteine-glutamine on mitochondrial oxidative damage was better than that of glycyl-glutamine.The protective effect of glutamine dipeptide on protein oxidative damage was measured at the level of biological macromolecules.The results showed that glutamine dipeptide could inhibit the formation of carbonyl groups and the decreased of thiol content;Selenocysteine-glutamine had a better protective effect on protein oxidative damage than glycyl-glutamine.