Immune versus natural selection: antibody aldolases with enzymic rates but broader scope.
Structural and mechanistic studies show that when the selection criteria of the immune system are changed, catalytic antibodies that have the efficiency of natural enzymes evolve, but the catalytic antibodies are much more accepting of a wide range of substrates. The catalytic antibodies were prepared by reactive immunization, a process whereby the selection criteria of the immune system are changed from simple binding to chemical reactivity. This process yielded aldolase catalytic antibodies that approximated the rate acceleration of the natural enzyme used in glycolysis. Unlike the natural enzyme, however, the antibody aldolases catalyzed a variety of aldol reactions and decarboxylations. The crystal structure of one of these antibodies identified the reactive lysine residue that was selected in the immunization process. This lysine is deeply buried in a hydrophobic pocket at the base of the binding site, thereby accounting for its perturbed pKa.
Barbas
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CF
The Skaggs Institute for Chemical Biology and the Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
Heine
A
A
Zhong
G
G
Hoffmann
T
T
Gramatikova
S
S
Björnestedt
R
R
List
B
B
Anderson
J
J
Stura
E A
EA
Wilson
I A
IA
Lerner
R A
RA
D000818:Animals; D017151:Antibodies, Catalytic / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D001665:Binding Sites; D002384:Catalysis; D018360:Crystallography, X-Ray; D003653:Decarboxylation; D019143:Evolution, Molecular; D005634:Fructose-Bisphosphate Aldolase / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D006019:Glycolysis; D006863:Hydrogen-Ion Concentration; D007114:Immunization; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D007700:Kinetics; D008239:Lysine / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D008958:Models, Molecular; D011487:Protein Conformation; D011730:Pyridoxal / Q000378:metabolism; D012641:Selection, Genetic; D013379:Substrate Specificity
D017151:Antibodies, Catalytic; D007140:Immunoglobulin Fab Fragments; D011730:Pyridoxal; C109536:antibody aldolase; D005634:Fructose-Bisphosphate Aldolase; D008239:Lysine