具有谷胱甘肽 ( GSH)结合部位的鼠抗体 3 H4 ( Ig M)经胃蛋白酶水解 ,产生分子量为 2 50 0 0的抗体 Fv片段 ,用荧光滴定法测定了它与 GSH的亲和常数 Ka=1 .1 7× 1 0 7L/ mol.该片段经苯甲基磺酰氟活化 ,再经Na HSe作用 ,其结合部位的丝氨酸被突变为谷胱甘肽过氧化物酶 ( GPX)的催化基团硒代半胱氨酸 .突变后的 Fv片段表现出很高的 GPX活性 ,其活力高达 2 50 0 U/μmol,称为 Fv抗体酶 .动力学分析表明 ,Fv酶的最适温度为 55℃ ,最适 p H为 7.0 ,催化机制为乒乓机制 ,米氏常数分别为 :Km( GSH) =4 .1 6× 1 0 - 3mol/ L,Km( H2 O2 ) =2 .8× 1 0 - 4 mol/ L The murine antibody 3 H4 (Ig M) with a glutathione (GSH) binding site was pepsin hydrolyzed to yield an Fv fragment of antibody with a molecular weight of 2 50 0 and its affinity constant with GSH was determined by fluorescence titration Ka = 1.7 × 10 7 L / mol. The fragment was activated by phenylmethylsulfonyl fluoride and then catalyzed by Na HSe, the serine at its binding site was mutated to glutathione peroxidase (GPX) Group of selenocysteine.The mutated Fv fragment showed high GPX activity, its activity as high as 2 50 0 U / μmol, called Fv antibody enzyme.Kinetic analysis showed that the optimum temperature of Fv enzyme was 55 ℃, the optimum p H is 7.0, the mechanism of the catalyst is the ping-pong mechanism, and the Michaelis constant are respectively: Km (GSH) = 4.16 × 10-3mol / L, Km 0 - 4 mol / L