| Texto completo | |
| Autor(es): |
Menegon, G
;
Loos, M
;
Chaimovich, H
Número total de Autores: 3
|
| Tipo de documento: | Artigo Científico |
| Fonte: | Journal of Physical Chemistry A; v. 106, n. 39, p. 9078-9084, OCT 3 2002. |
| Citações Web of Science: | 20 |
| Resumo | |
Phosphate esters are key compounds in important biological reactions, One family of enzymes, PTPases, catalyze the dephosphorylation of tyrosine residues from other proteins by a cystein side-chain nucleophilic attack at tyrosin phosphate. Very little is known about the intrinsic reactivity of thiol nucleophiles with phosphor-us centers. To explore this important reaction, we have performed ab initio calculations on the trimethyl phosphate ester (TMP) thiolysis by (CH3S)(-). Results in the gas phase indicate that attack at TMP carbon is essentially predominant over phosphorus. Mechanisms are A(n)D(n) and exoergic for reaction at carbon and A(n) + D-n with large activation barriers and endoergic reaction for attack on phosphorus. A trigonal-bipyramid intermediate was formed upon (CH3S)(-) reaction at phosphorus and two different and competitive pathways were found for the elimination of methoxide from this intermediate. One of the elimination pathways is positioned in-line to the thiol group, as proposed in the enzymatic mechanism. If PTPases work by the same mechanism as the gas-phase reaction, these enzymes should drastically lower the activation barriers for attack at phosphorus. (AU) | |
| Processo FAPESP: | 99/04072-7 - Mecanismos da tiólise de ésteres de fosfato: modelos da fosfatase ácida SH-dependente |
| Beneficiário: | Guilherme Menegon Arantes |
| Modalidade de apoio: | Bolsas no Brasil - Doutorado |