Chemical modification of a catalytic antibody that accelerates the hydrolysis of carbonate esters

Catalytic antibody, 4A1, catalyzes the hydrolysis of p-nitrophenyl alkyl carbonate. To determine the amino acid residues related to the catalytic activity of the antibody, we studied the effect of Tyr-, Trp-, and Lys-selective reagents on the catalytic activity and determined the amino acid sequences around the modified amino acid residues. We found that the Tyr-selective reagent is the most effective one and the modification of one Tyr residue results in the complete loss of the catalytic activity. The modified Tyr residue is identified to be Tyr-32 in the CDR-1 of the L chain.