Mechanism of Formation of the Internal Aldimine in Pyridoxal 5 '-Phosphate-Dependent Enzymes

• Tipo: Artigo em Revista Científica Internacional
• Data: 2011

Autores

Eduardo F Oliveira (Autor) Outra; Nuno M F S A Cerqueira (Autor) FCUP; Pedro A Fernandes (Autor) FCUP; Maria J Ramos (Autor) FCUP

Revista

Título: Journal of the American Chemical Society

Vol. 133

Páginas: 15496-15505

ISSN: 0002-7863

Editora: American Chemical Society

Indexação

ISI Web of Knowledge - 78 Citações

Scopus - 78 Citações

Classificação Científica

FOS: Ciências exactas e naturais > Química

Outras Informações

ID Authenticus: P-002-KJX

DOI: 10.1021/ja204229m

Abstract (EN): In this paper we studied the mechanism of formation of the internal aldimine, a common intermediate to most pyridoxal 5'-phosphate (PLP)-dependent enzymes. A large model based on the crystal structure from the human ornithine decarboxylase (ODC) enzyme was constructed and in total accounts for 504 atoms. The reaction mechanism was investigated using the ONIOM methodology (B3LYP/6-31G(d)//AM1), and the final energies were calculated with the M06/6-311++G(2d,2p)//B3LYP/6-31G(d) level of theory. It was demonstrated that the reaction is accomplished in three sequential steps: (i) the nucleophilic attack of Lysine69 to PLP, (ii) the carbinolamine formation, and (iii) a final dehydration step. For the carbinolamine formation, several mechanistic hypotheses were explored, and the preferred pathway assigns a key role for the conserved active site Cys360. The overall reaction is exergonic in -9.1 kcal/mol, and the rate-limiting step is the dehydration step (E(a) = 13.5 kcal/mol). For the first time, we provide an atomistic portrait of this mechanism in an enzymatic environment. Moreover, we were able to assign a novel role to Cys360 in the ODC reaction mechanism that was never proposed.

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Nº de páginas: 10