title: Different Effects of Mg and Zn on the Two Sites for Alkylammonium Compounds in Pseudomonas aeruginosa Phosphorylcholine Phosphatase.
abstract: Pseudomonas aeruginosa phosphorylcholine phosphatase (PchP) catalyzes the hydrolysis of phosphorylcholine (Pcho), is activated by Mg(2+) or Zn(2+), and is inhibited by high concentrations of substrate. This study has shown that PchP contains two sites for alkylammonium compounds (AACs): one in the catalytic site near the metal ion-phosphoester pocket, and the other in an inhibitory site responsible for the binding of the alkylammonium moiety. The catalytic mechanism for the entry of Pcho in both sites and Zn(2+) or Mg(2+) follows a random sequential mechanism. However, Zn(2+) is more effective than Mg(2+) at alleviating the inhibition produced by the entry of Pcho or different AACs in the inhibitory site. We postulate that Zn(2+) induces a conformational change in the active center that is communicated to the inhibitory site, producing a compact or closed structure. In contrast, Mg(2+) produces a relaxed or open conformation.
authors.affiliation: Departamento de Biología Molecular, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Ruta Nacional 36 Km 601, Río Cuarto, 5800 Córdoba, Argentina.
authors.forename: Lisandro Horacio
authors.initials: LH
authors.lastname: Otero
authors.forename: Paola Rita
authors.initials: PR
authors.lastname: Beassoni
authors.forename: Cristhian
authors.initials: C
authors.lastname: Boetsch
authors.forename: Angela Teresita
authors.initials: AT
authors.lastname: Lisa
authors.forename: Carlos Eduardo
authors.initials: CE
authors.lastname: Domenech