化学修饰抗体增加模拟酶的GPX活性

将丝氨酸共价偶联到兔抗人ＩｇＭ（Ｆｃμ）抗体上，以增加抗体结合部位丝氨酸残基含量．在中性条件下，丝氨酸被对苯甲基磺酰氟活化，再经ＮａＨＳｅ亲核取代，将丝氨酸诱变为硒代半胱氨酸（ＳｅＣｙｓ）．其谷胱甘肽过氧化物酶（ＧＰＸ）活性由未增加丝氨酸前的诱变抗体的７０Ｕ／μｍｏｌ提高到２１８Ｕ／μｍｏｌ，其活性为模拟物ＰＺ５１的２００多倍．

Increasing GPX Activity of Imitating Enzyme by Chemically Modifying Antibody

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.