Chemistry Reference
In-Depth Information
Scheme 4.12 Catalytic antibody 1F7 was raised against the transition
state analog 28 and possesses modest chorismate mutase activity. It
can complement a permissive yeast strain that is auxotrophic for
phenylalanine and tyrosine by replacing the natural enzyme (CM) in the
shikimate biosynthetic pathway.
retro-aldol and retro-Michael reactions (Scheme 4.11) [66]. Detoxification of otherwise
toxic substances is also feasible, as shown by the protection of rats from cocaine-in-
duced seizures and death by a cocaine-hydrolyzing antibody [67].
Successful production of immunoglobulins in microorganisms such as Escherichia
coli and yeast opens the door to additional in vivo applications. Intracellular biosynth-
esis of tailored antibody catalysts could confer new properties on these organisms,
such as pesticide resistance or novel biosynthetic capabilities. Experiments with an
anti-
28
antibody possessing modest chorismate mutase activity [68] show that they
can replace natural enzymes in cellular metabolism. When produced cytoplasmically
at high concentrations in a chorismate mutase deficient yeast strain, the Fab fragment
of this catalyst reconstitutes the shikimate biosynthetic pathway leading to the aro-
matic amino acids tyrosine and phenylalanine (Scheme 4.12), conferring a substantial
growth advantage under auxotrophic conditions [69]. Although efforts to direct the
evolution of this primitive antibody through cycles of mutagenesis and genetic selec-
tion have not provided substantially more active clones, they have identified the heavy
chain as the minimal domain needed for function in vivo, which is consistent with the
observation that this chain contributes over 90% of the contacts with the bound tran-
