Reactive Immunization with the Simple Diketone Derivative

1 Reactive Immunization with the Simple Diketone Derivative 

Historically, Frank Westheimer used 1,3-diketones as mechanistic probes of the enzyme acetoacetate decarboxylase [6]. The active site of acetoacetate decarboxylase has a nucleophilic lysine e-amino group and forms a Schiff base in its catalytic cycle. In his studies, the active site lysine e-amino group of this enzyme reacted covalently vith the 1,3-diketones. Later 1,3-diketones vere used as modification reagents for the nucleophilic lysine e-amino groups of many enzymes [7]. 

Antibodies prepared from hybridomas derived after immunization vith 1,3-diketone hapten 1-carrier protein conjugate vere screened for their capacity to form the stable enaminone (absorption maximum = 316 nm) 

For the aldol reaction of acetone and aldehyde 3 at pH 7.5, aldolase antibodies 38C2 and 33F12 had (kcat/km)/kuncat 10 - The efficiency of catalysis is largely because of an entropic advantage in the antibody-catalyzed reaction, vhich is reflected as a high effective molarity, kcat/kuncat 10 m. 

With the best substrates identified to date for the retro-aldol reaction [8-10], the catalytic proficiency (kcat/K )/k ncat 6 x 10 . The catalytic efficiency (kcat/km) of these aldolase antibodies vith these substrates is only 20-40-fold below that of the most studied aldolase enzyme, fructose-1,6- 

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