Chapter 27. Catalytic Antibodies

Abstract

Enzymes are proteins that have evolved to catalyze the biochemical reactions. They do so by stabilizing the transition state of the reaction, thus providing a lower energy pathway for the conversion of substrate to product. Accordingly, it has been proposed that the active site structure of an enzyme has evolved to be more complementary to the transition state structure rather than the ground state structures of substrates or products. Given the adaptable nature of the antibody molecule, it is perhaps not surprising that the antibodies that bind transition state (TS) analogs can be produced from the vertebrate immune response. These antibodies are called catalytic antibodies. They behave similarly to enzymes in that they show saturation kinetics, substrate selectivity, and accelerate the rate of reaction over the uncatalyzed background reaction. As a technology, catalytic antibodies offer a potential source of laboratory-designed enzymes for possible applications as research tools or therapeutics. Antibodies, with combining sites that are complementary to stable transition state analogs, are catalytically active in the same way as natural enzymes. The monoclonal antibody technology has made it possible to obtain gram-quantities of homogeneous antibody samples that are crucial for the kinetic characterization of antibody catalysis. The major research emphasis in this field in recent times has been to define the chemical scope of antibody catalysis and determine the classes of chemical reactions that are amenable to antibody catalysis through transition state analog design. It is now clear that the scope of antibody catalysis is quite broad and it is now reasonable to assume that any reaction, for which a bonafide transition state analog can be synthesized, is anticipated to produce an antibody catalyst with some catalytic activity.