Future efforts in the study of antibody catalysis will be directed at (1) characterizing the available abzymes kinetically and structurally and (2) exploring the scope for catalysis of acyl transfer and other reaction types. The role and identity of catalytic groups in the esterolytic antibodies may be revealed by the measurement of the pH dependence of, and solvent isotope effects on the rate. Stopped-flow kinetics will be employed to study the pre-equilibrium steps and determine their relative rates. Active site residues may be identified by affinity labeling with alkylative substrate analogs, followed by partial digest of the protein and peptide analysis. In collaboration with molecular biologists the complete amino acid sequence of these antibodies may be deduced by sequencing the cloned cDNA. A comparison of these data from esterolytic antibodies with high activity (Kcat 20 s-1) and those with moderate activity would highlight the factors important for efficient catalysis. Sequence comparisons to highly homologous antibodies may also reveal important structural factors. An approach of incremental difficulty will be pursued in attempting to derive new catalytic antibodies. Hydrolysis of certain alkyl esters will be addressed using alkyl phosphonates for immunizations. The hydrolysis of aryl amides that are relatively reactive may be approached with suitable phosphomamidates as haptins. Similar activity will be sought by using cyclic boronate- amine adducts as analogs of amide hydrolysis intermediates. Finally, systems will be designed to explore the feasibility of accelrating bimolecular reactions with antibodies. Multisubstrate analogs for reduction-oxidation processes will be prepared. Antibodies that bind two ligands simultaneously may be assessed as redox catalysts. The preparation of semisynthetic abzymes will be pursured. A redox process will be studied between a reducing ligand and an oxidative factor that is attached covalently to the antibody combining site.
