Increasing GPX Activity of Imitating Enzyme by Chemically Modifying Antibody
LIU Junqiu,SHI Chengbo,JIANG Mingsou,LUO Guimin,YAN Ganglin
(The National Laboratory of Enzyme Engineering,Jilin University,Changchun 130023) SHEN Jiacong (Key Laboratory for Supermolecular Structure & Spectra of Jilin University,Changchun 130023
Abstract：Glutathione peroxidase(GPX,EC 1.11.1.9)is a selenoenzyme.It can prevent biomembranes from oxidative damage and has potentialities to cure some diseases.The artificial imitation of GPX becomes important because of its instability and limited availability.In order to introduce selenocysteine,the catalytic group of GPX,into the binding site of antibody,serines were covalently connected to rabbit anti human IgM(Fcμ)with glutaraldehyde.The optimal amount of glutaraldehyde(1%, W/W )was found to be 50 120 μl/mg antibody.The serines in specific sites of IgM were selectively activated by phenylmethylsulfonylfluoride(PMSF)in neutral condition and substituted by sodium hydrogen selenide.The optimal amount of PMSF and NaHSe was found to be 100 mg/L and 50 mg/L,respectively.The amount of selenuim in the modified antibody was determined to be 6 8 mole per mole of antibody.The modified antibody exhibited higher GPX activity,which was 218 U/μmol,than that of unmodified antibody.The GPX activity was 3 times as great as that of the latter and 200 times more than that of PZ51.This method may be utilized to increase the GPX activities of abzymes.
