Alkaline Phosphatases: in Silico Study on the Catalytic Effect of Conserved Active Site Residues Using Human Placental Alkaline Phosphatase (PLAP) As a Model Protein.

The metalloenzymes from the alkaline phosphatase (AP) superfamily catalyze the hydrolysis and transphosphorylation of phosphate monoesters. The role of several amino acids highly conserved in the active site of this family of enzymes was examined, using human placental AP (PLAP) as a model protein. By employing an active-site model based on the X-ray crystal structure of PLAP, mutations of several key residues were modeled by quantum mechanical methods in order to determine their impact on the catalytic activity. Kinetic and thermodynamic estimations were achieved for each reaction step of the catalytic mechanism by characterization of the intermediates and transition states on the reaction pathway, and the effects of mutations on the activation barriers were analyzed. A good accordance was observed between the present computational results and experimental measurements reported in the literature.