Fast Hydrolysis of an Aliphatic Amide at Neutral pH and Ambient Temperature. A Peptidase Model

Article abstract of DOI:10.1021/ja00228a031

An intramolecular-catalysed cleavage of an aliphatic amide under biological conditions (ambient temperature, neutral pH, absence of alien transition metals) was found to occur with the fastest rate yet recorded for such a reaction: t_1/2 = 8 min (pD=7.05, 21.5 deg C) and an effective molarity EM>1E14 M.The peptidase "model" has a carboxyl oxygen perched above the plane of the amide carbonyl at a van der Waals contact distance of 2.8 Angstroem.The carboxyl is poised for synchronous nucleophilic attack and proton delivery.Evidence (based on the observation that the amide actually cleaves much faster than the corresponding methyl ester) suggest that proton transfer plays a key role in the rate-determining step.The results show that an enzyme need not employ esoteric mechanisms to cleave an unreactive entity such as an amide.If the enzyme merely positions a carboxyl adjacent to an amide substrate with the geometry established in the "model", most of the necessary catalytic power would be achieved.