Kemp elimination reactions antibody

Acevedo, O. Role of water in the multifaceted catalytic antibody 4B2 for allylic isomerization and Kemp elimination reactions. J. Phys. Chem. B 2009,113,15372-81. 

Figure 14 (a) Elimination reaction catalyzed by antibodies 43D4 and 3D12 raised against the quaternary ammonium 17 and (b) Kemp reaction catalyzed by antibody 34E4 raised against the amidinium 18. 

Kemp elimination was used as a probe of catalytic efficiency in antibodies, in non-specific catalysis by other proteins, and in catalysis by enzymes. Several simple reactions were found to be catalyzed by the serum albumins with Michaelis-Menten kinetics and could be shown to involve substrate binding and catalysis by local functional groups (Kirby, 2000). Known binding sites on the protein surface were found to be involved. In fact, formal general base catalysis seems to contribute only modestly to the efficiency of both the antibody and the non-specific albumin system, whereas antibody catalysis seems to be boosted by a non-specific medium effect. 

Figure 2 Free-energy profile for the Kemp elimination of 5-nitro-benzisoxazole by antibody 4B2. The reaction coordinate for the proton transfer is r(0-H)-r(H-C) with r(0-H)+r(H-C)=2.85 A. Maximum free-energy values are truncated to 30 kcal/mol for clarity.

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