Nucleophilic and general acid catalysis at physiological pH by a designed miniature esteraseElectronic supplementary information (ESI) available: NOESY and TOCSY spectra; Table with NMR assignments and observed NOEs; complete set of kinetic data for Art-Est catalysis; mass spectrum of fumaryl-Art-Est intermediate; rate constants for the spontaneous and catalysed ester hydrolysis. See http://www.rsc.org/suppdata/ob/b4/b404730c/. Coordinates for the structure of Art-Est have been deposited in the Brookhaven Protein Data Bank, code 1v1d.