Isomerization of Delta(5)-Androstene-3,17-dione into Delta(4)-Androstene-3, 17-dione Catalyzed by Human Glutathione Transferase A3-3: A Computational Study Identifies a Dual Role for Glutathione

• Tipo: Artigo em Revista Científica Internacional
• Data: 2014

Autores

Daniel F A R Dourado (Autor) Outra; Pedro Alexandrino Fernandes (Autor) FCUP; Bengt Mannervik (Autor) Outra; Maria Joao Ramos (Autor) FCUP

Revista

Título: Journal of Physical Chemistry A

Vol. 118

Páginas: 5790-5800

ISSN: 1089-5639

Editora: American Chemical Society

Indexação

ISI Web of Knowledge - 11 Citações

Scopus - 11 Citações

Classificação Científica

FOS: Ciências exactas e naturais > Química

Outras Informações

ID Authenticus: P-009-R2A

DOI: 10.1021/jp410810q

Abstract (EN): Glutathione transferases (GSTs) are important enzymes in the metabolism of electrophilic xenobiotic and endobiotic toxic compounds. In addition, human GST A3-3 also catalyzes the double bond isomerization of Delta 5-androstene-3,17-dione (Delta(5)-AD) and Delta(5)-pregnene-3,20-dione (Delta(5)-PD), which are the immediate precursors of testosterone and progesterone. In fact, GST A3-3 is the most efficient human enzyme known to exist in the catalysis of these reactions. In this work, we have used density functional theory (DFT) calculations to propose a refined mechanism for the isomerization of Delta(5)-AD catalyzed by GST A3-3. In this mechanism the glutathione (GSH) thiol and Tyr9 catalyze the proton transfer from the Delta(5)-AD C4 atom to the Delta(5)-AD C6 atom, with a rate limiting activation energy of 15.8 kcal.mol(-1). GSH has a dual function, because it is also responsible for stabilizing the negative charge that is formed in the 03 atom of the enolate intermediate. The catalytic role of Tyr9 depends on significant conformational rearrangements of its side chain. Neither of these contributions to catalysis has been observed before. Residues Phe10, Leul11, Ala 208, and Ala 216 complete the list of the important catalytic residues. The mechanism detailed here is based on the GST A3-3:GSH:Delta(4)-AD crystal structure and is consistent with all available experimental data.

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Nº de páginas: 11