Abstract: The mouse McAb3H4 with a glutathione combining site was digested by pepsin to produce an antibody Fv fragment with molecular weight of 25000 . The association constant of Fv to GSHwas found to be 1.17×10⁷ L/mol by using titration of fluorescence quenching. After activation with PMSF, the active serine in the binding site of Fv was mutated to the selenocysteine which is the catalytic group in the natural glutathione peroxidase. The Se containing Fv fragment shows a high GPXcatalytic activity of 2500 U/μmol. Kinetic study shows that the optimum temperature is 55 ℃ and pHis 7.0 . The Fv enzyme has the similar catalytic mechanism to that of the natural GPX. The K_m(GSH) of Fv enzyme abzyme is 4.16×10^-3 mol/Land K_m(H₂O₂) is 2.8×10^-4mol/L.

Key words: Glutathione peroxidase (GPX), Chemical mutation, Antibody Fv fragment, Abzyme, Artificial enzyme