ANTIBODY BAIT AND SWITCH CATALYSIS - A SURVEY OF ANTIGENS CAPABLE OF INDUCING ABZYMES WITH ACYL-TRANSFER PROPERTIES

Antibodies have been shown to catalyze acyl-transfer reactions. Various antigens have been applied to these hydrolytic reactions, but typically all encompass the same theme of incorporating a monoanionic phosphonate/phosphonamidate. To expand the scope and capabilities of these abzymes, we have directed our attention toward new strategies in antigen design. One method, which we have termed ''bait and switch'' catalysis, uses haptens to elicit amino acid(s) within the binding pocket of an antibody that can accelerate hydrolysis. We reported initial success of this methodology utilizing the cationic hapten 1 for obtaining abzymes that hydrolyzed benzoate ester 6. In addition, we showed how the structurally identical but neutral hapten 2 was unable to induce catalytic antibodies. To further identify those factors critical in the generation of hydrolytic abzymes via our bait and switch methodology, we have (1) designed and synthesized three new homologues of 1 in which we have varied the type of charge/no charge and its location, (2) screened and identified catalytic antibodies from these antigens, (3) determined affinity constants of a number of these monoclonal antibodies (catalytic and noncatalytic) for their respective haptens and possible substrates (ester/amide), (4) performed steady-state kinetics, inducing a pH-rate profile on one of these abzymes, and (5) used chemical modifying reagents to identify which amino acid residue(s) are involved in these catalytic processes.