Analyzing Kirby’s amine olefin—a model for amino acid ammonia lyases

Ab initio and DFT calculations on the ring-closing reaction of Kirby’s amine olefin (ammonia lyase enzyme model) reveal that the process involves two consecutive steps: proton transfer from a molecule of water to the carbon–carbon double bond followed by nucleophilic attack of the amine nitrogen onto the second carbon of the double bond. Further, they indicate that the second step in the process is barrier less due to the combination of the release in strain energy upon conversion of the reactant to the product and, the proximity orientation of the nucleophile to the electrophile. Effective molarity (EM) calculations establish that Kirby’s amine olefin process undergoes ring-closing at a rate that is comparable to the rates of reactions catalyzed by the most efficient enzymes.