Catalytic Mechanism of a New Catalytic Antibody L-chain, L-zyme.

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Two hybridoma cells (03-1,13-1), that produce monoclonal antibody against TCPP,were obtained. Genes for both H and L chains of monoclonal antibodies were cloned, sequenced and overexpressed using E.coli as a host. It was found that the independent antibody L chains from both Mab03-1 and Mab13-1 have specific interaction with TCPP.The antibody L chain from Mab13-1 exhibits much higher peroxidase activity than TCPP Fe (III) alone. Furthermore, optimum temperature of the peroxidase reaction by the complex of 13-1L chain and TCPP Fe (III) was 90ﾟC,while that of the TCPP Fe (III) alone was 60ﾟC.Characterization of the mutant catalytic antibodies revealed that the hydrophobic region in the constant region (residue number 115-146) is important for high thermostability and the hydrophilic region (residue number 147-189) is important for high activity. Tertiary structure of this L cahin catalytic antibody was predicted using a computer software AbM and the structure was compared with the strucure of the peroxidase from Arthromyces ramosus. Important His and Arg residues for the calytic activity were conserved in the antigen binding site of the L chain (His38, His94 and Arg96) and they were found in complementarity determining regions (CDR).