Antibody 03-1, which was prepared by immunization with meso-tetrakis(4-carboxyphenyl)porphyrin (TCPP) conjugate, has been found to bind strongly to Mn(III)-TCPP and Fe(III)-TCPP complexes with dissociation constants of 4.1 x 10(-7) and 1.5 x 10(-7) M, respectively, although other monoclonal antibodies raised against TCPP did not bind to these TCPP-metal complexes. The complexes of antibody 03-1 with Mn(III)-TCPP and Fe(III)-TCPP were found to catalyze oxidation of pyrogallol selectively. A Lineweaver-Burk plot for the oxidation of pyrogallol by the antibody-Fe-TCPP complex showed K-m = 4.0 mM and k(cat) = 50 min(-1). Studies on the effect of the molar ratio of the antibody to metalloporphyrin on the catalytic activity showed that a 1:1 complex was the most effective for the reaction. The effect of salt (NaCl) on the reaction showed that electrostatic interaction between the antibody and the metalloporphyrin was important for the reaction. The antibody-metalloporphyrin complexes are stable enough to show catalytic activity in the presence of an excess amount of H2O2.