INFIQC   05475
INSTITUTO DE INVESTIGACIONES EN FISICO- QUIMICA DE CORDOBA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Quantum mechanical study on the catalytic activity of human placental alkaline phosphatase.
Autor/es:
BOROSKY, GABRIELA L.
Lugar:
Villa Carlos Paz
Reunión:
Conferencia; 13th Latin American Conference on Physical Organic Chemistry, CLAFQO-13; 2015
Resumen:
Alkaline phosphatases (APs) are metalloenzymes found in many species (from bacteria to man),[1] which catalyze the hydrolysis of phosphomonoesters with release of inorganic phosphate and an alcohol.[2] The catalytic mechanism involves activation of a serine residue, formation of a covalent phosphoseryl intermediate, hydrolysis of the phosphoserine by an activated water molecule, and release of the phosphate product or its transfer to a phosphate acceptor. Human placental AP (PLAP) is one of the four AP isozymes found in human. In this work computational calculations were performed with the aim of achieving a better understanding of the catalytic activity of PLAP. The active site of the enzyme was modelled according to the crystal structure reported in the Protein Data Bank. The reaction steps of the catalytic mechanism were evaluated within the active site for four substrates (two aromatic and two aliphatic phosphomonoesters), and comparisons were made considering the effect of the substrate on the catalytic activity. Quantum-chemical methods were applied by employing a two-layer ONIOM(QM:QM) procedure. In this way, density functional theory (DFT) computations were carried out for the reacting system (phosphomonoester substrate and catalytic serine), as well as for the metal cations, their ligands, and the water molecules involved in the catalytic mechanism, while semiempirical methods were employed for the rest of the atoms. The influence of the protein environment was taken into account by means of the IEFPCM method. Free energies of activation (ΔG≠) and of reaction (ΔGr) were computed for each step of the mechanism of catalysis. Mechanistic variations according to the nature of the substrate (an aryl or alkyl phosphate) were examined. References: [1] R. B. McComb, G. N. Bowers, S. Posen, in Alkaline Phosphatases, Plenum Press, New York, (1979) 986 [2] J. H. Schwartz, F. Lipmann, Proc. Natl. Acad. Sci. USA 47 (1961) 1996.