Computational study concerning the catalytic mechanism of human placental alkaline phosphatase.

BOROSKY, GABRIELA L.

Antigua

Conferencia; Zing Computational Chemistry Conference 2009; 2009

Alkaline phosphatases (APs) are metalloenzymes found in many species from bacteria to man.1 They catalyse the hydrolysis of phosphomonoesters with release of inorganic phosphate and alcohol.2 The catalysis involves the activation of the catalytic serine, the formation of a covalent phosphoseryl intermediate, the hydrolysis of the phosphoseryl by an activated water molecule, and the release of the phosphate product or its transfer to a phosphate acceptor. PLAP is one of the four AP isozymes found in human. The active site of PLAP was modelled according to the crystal structure reported in the Protein Data Bank (Figure 1), and the reaction steps of the catalytic mechanism were evaluated within the active site environment. Quantum-chemical calculations were performed employing the ONIOM procedure. In this study, DFT computations were carried out for the reacting phosphomonoester and catalytic serine, as well as for the metal cations, their ligands, and the water molecules involved in the catalytic mechanism. On the other hand, the semiempirical PM3MM hamiltonian was applied for the rest of the atoms. Free energies of activation (?¢G??) and of reaction (?¢Gr) were evaluated for each step of the mechanism of catalysis.