Generation of Tailor-made Biocatalysts Using Immune System.

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From the first report of catalytic antibodies in 1986, a variety of the antibodies has been generated and found to catalyze chemical reactions from peri-cyclic reactions to amido-bond hydrolyses. Most of them are elicited by immunization of transition-state analogs. However, unfortunately, the catalytic activities are not sufficient. Therefore, we take advantage of catalytic power of cofactors. In this work, we aim to incorporate synthetic cofactors into antibody-combining sites to generate catalytic antibodies.A bi-functional hapten was designed and synthesized to elicit both substrate and cofactor binding sites in antibody-combining sites. After immunization to mice with the carrier protein (KLH)-hapten conjugate, we isolated 50 monoclonal antibodies by hybridoma technology. Of the antibodies, 22 were found to be catalytic in acyl-transfer reactions of p-nitrophenol ethyl esters with synthetic co-factors attaching alcohol, amino, and sulfur groups. The kinetic parameters (K_m, VK_<max>,k_<cat> ) for the most active antibodies (27C1 and 25E2) were examined in detail. Furthermore, antibody 27C1 also catalyzed elimination reactions of β-fluoroketone to give the corresponding enone when the synthetic co-factor attaching carboxylate was used. In this work, we have demonstrated generating catalytic antibodies with synthetic cofactors and controlling the catalytic activity by changing the co-factors. Because antibodies can be generated virtually any molecule of interest, combination of antibodies and co-factors should lead to a new class of biocatalysts with tailor-made specificity and reactivity.