This paper reports the synthesis of rationally designed polypeptides that catalyze the decarboxylation of oxaloacetate via an imine intermediate. The authors det. the secondary structures of the polypeptides by two-dimensional NMR spectroscopy. The authors are able to trap and identify intermediates in the catalytic cycle, and to explore the kinetics in detail. The formation of the imine by the authors' artificial oxaloacetate decarboxylases is three to four orders of magnitude faster than can be achieved with simple amine catalysts: this performance rivals that of typical catalytic antibodies. [on SciFinder (R)]