The Role Of Tyrosine Residues In BSA In The Inhibition Of Heme-injured Cells By BSA

Heme is a widespread protein cofactor in vivo. It is the main stable structure and protein cofactor of hemoglobin, myoglobin, brain protein, etc. So it plays a very important physiological function in living organisms. However, when the body occurs severe hemolysis in pathological condition, the concentration of heme exceeds the tolerance of body defense system. Too much free heme will promote lipid peroxidation, as well as protein and DNA oxidative damage. When nitrite and H2O2 are presence, heme can also catalyze protein tyrosine nitration, leading to further damage to body.Serum albumin is the most abundant carrier protein in plasma, and it palys a series of very important physical functions in vivo. The unique molecular structure of SA promotes it to bind and transport a wide variety of endogenous and exogenous compounds in the circulaition of the blood system. SA can bind to heme tightly, and involved in the metabolism and detoxification of heme.However the exact detoxification mechanism is not fully clear.In this paper, we study the role of tyrosine residues in BSA to inhibit cell damage induced by heme. Fist of all,we used iodine to react with BSA and get tyrosine residues modifed BSA(BSA-T).and the was verified by UV-vis spectrum.Then the TMB method is used to detect the peroxidase activites of heme-BSA and heme-(BSA-T).Then the mice neuroblastoma SHSY-5Y cells were used as a cell model, and MTT method and Hoechst33258 were adopt to detect the protect effects of BSA and BSA-T on heme-H2O2-NO2- system induced cell viability and apoptosis. Then immunofluorescence experiment and western blotting were used to determine the effects of BSA and BSA-T on heme-H2O2-NO2- system induced cell protein nitration and oxidation respectively. Finally, TAB method was used to the effects of BSA and BSA-T on heme-H2O2-NO2- system induced lipid peroxidation in cells.The results showed that the modification of tyrosine residues in the BSA doesn't affect the peroxidase activity of heme-BSA. The the presence of H2O2 and heme will lead to cell damage, and increase the degree of protein oxidation,niration and lipid peroxidation in the cell, the addition of NO2- will further aggravate the cell damage, both BSA and BSA-T are all have some degree of inhibition to a series of injuries in the cell caused by heme-H2O2-NO2- system, but BSA is more effective than BSA-T. In conclusion, tyrosine residues play an important role in BSA inhibiting heme to catalyze cell oxidation and nitration.