AREAS RELATED TO ENZYME CATALYSIS - New Trends in Enzyme Catalysis and Biomimetic Chemical Reactions - page 165

Though the values of the Michaels complex for reactions
catalyzed by natural enzymes and catalytic antibodies were found to be of the same order
of magnitude, the catalytic constants for CAs commonly fold lower than that
for correspondent enzymes. Experimental ratio values for CAs ranges within
while these values for similar enzymatic reactions can reach 10 17 .
Examples of reactions catalyzed by catalytic antibodies, structures of corresponding
transition states and haptens are presented in Figs. 5.1 and 5.2.
In the case of the oxy-Cope rearrangement, NOE and X-ray structural analysis
indicated preorganization of the normally extended hexadien substrate into cyclic
conformation, ligand recognition is mediated by van der Waals contacts, with
aromatic rings and hydrogen bonding. The necessity of protoporphyrin IX distortion in
the binding site of an antibody catalyzed in complexation with was proved by the
X-ray structural analysis. The non-planar N-methylated porphyrins, which are inhibitors
of ferrochelatase, makes extensive contacts with binding sites of the correspondent
antibody.
The use of hydroxylated hapten mimicking the transition state in hydrolysis of the
organophosphorus poisoning compound produces an antibody capable of hydrolyzing
warfare nerve agents such as Sarin and Soman in vivo (Vayron, 2000a,b). Another recent
example of antibody catalysis is the formation of steroid ring A of the lanosterol nucleus
(Hasserodt et al., 2000). Antibodies generated by immunization with an 4-aza-steroid
aminoxide hapten initiated the cationic cyclization of an oxidosqualene derivative.
Current and potential applications of catalytic antibodies in reactive immunization,
therapy, biochemical analysis and biotechnology have been discussed (Schultz and
Lerner, 1995; Rader and List, 2000; Blackburn and Garcon, 2000; Hilvert, 2000; Rader
and List, 2000; Blackburn and Garcon, 2000; Vayron , 2000a,b).