An analog-ligand having a conformation that substantially corresponds to the conformation of a hydrolytic transition state of an amide or ester reactant ligand is used to produce receptor molecules of predetermined specificity. The receptor molecules include an antibody combining site that binds to the analog-ligand and also to a reactant ligand and thereby stabilizes the tetrahedral carbon atom of the amide or ester hydrolysis transition state of that reactant ligand to catalytically hydrolyze the reactant ligand at a predetermined site.