SYNTHESIS, STRUCTURE AND ACTIVITY OF ARTIFICIAL, RATIONALLY DESIGNED CATALYTIC POLYPEPTIDES

BIOLOGICAL macromolecules with catalytic activity can be created artif icially using two approaches. The first exploits a system that selects a few catalytically active biomolecules from a large pool of randomly generated (and largely inactive) molecules. Catalytic antibodies1 and many catalytic RNA molecules2 are obtained in this way. The second in volves rational design of a biomolecule that folds in solution to pres ent to the substrate an array of catalytic functional groups3-8. Here we report the synthesis of rationally designed polypeptides that catal yse the decarboxylation of oxaloacetate via an imine intermediate. We determine the secondary structures of the polypeptides by two-dimensio nal NMR spectroscopy. We are able to trap and identify intermediates i n the catalytic cycle, and to explore the kinetics in detail. The form ation of the imine by our artificial oxaloacetate decarboxylases is th ree to four orders of magnitude faster than can be achieved with simpl e amine catalysts: this performance rivals that of typical catalytic a ntibodies.