Theoretical study on pyridoxal 5′-phosphate -catalyzed decarboxylation reaction of L-alanine: mechanism, role of protonated pyridine moiety
摘要
In this article, we have theoretically studied the L-Alanine decarboxylation reaction catalyzed by pyridoxal 5′-phosphate-based aldimine (denoted as PLP) at M06-2X-D3/6-311G(d,p)/IEFPCM level of theory. The reaction went through amine acetal formation, decarboxylation and catalyst regeneration procedures, and the rate-determining step is decarboxylation reaction with 28.2 kcal/mol activation Gibbs free energy barrier. The role of protonated pyridine (PyH+) moiety of PLP was investigated by theoretically studying isoelectronic species (IES)-catalyzed reaction, PLP is more catalytic active than IES because PLP can lower the activation free energy barrier by means of increasing aromaticity of PyH+ moiety but the phenyl moiety of IES cannot, indicating the PyH+ moiety of PLP cannot be replaced arbitrarily.