Abstract: Three selenium-containing catalytic antibodies mHB4, mHB5 and mHB7, which acted as mimics of cytosolic glutathione peroxidase(cGPX), were prepared by chemically introducing selenium into monoclonal antibodies HB4, HB5 and HB7. HB4, HB5 and HB7 were raised against a GSH derivative GSH S DNP dibenzyl ester. The cGPX activity of mHB4, mHB5, mHB7 were 170, 1 867, 32 U/μmol, respectively. The cGPX activity of mHB5 was 0.32 fold of natural rabbit liver cGPX and 1.51 fold of m4A4. About two atoms of selenium existed in each of mHB5 molecule determined by inductively-coupled plasma/mass spectroscopy(ICP-MS). The optimal activity of mHB5 was at between pH 8.4 and 8.8. The reaction catalyzed by mHB5 involved a Ping Pong mechanism. At pH 7.0 and 37 ℃, the apparent second order rate constants for reaction of mHB5 with H₂O₂ and t ROOH were as followed: _k+1 (H₂O₂)=9.71×10⁶ L/(mol·min), _k+1 ( t ROOH)=5.99×10⁵ L/(mol·min). Rate accelerations( k_cat / K_m/ k_uncat ) 9.8×10⁶ and 3.7×10⁵ fold those of the uncatalytic reaction were observed.

Key words: Monoclonal antibody, Selenium-containing catalytic antibody, Glutathione peroxidase