Mg2+, Zn2+ and Cu2+ are activators and antiinhibItors of P. aeruginosa phosphorylcholinephosphatase

OTERO, LH; BEASSONI, PR; DOMENECH, CE

Mar del Plata - Bs As

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2007

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Phosphorylcholine phosphatase (PchP) from P. aeruginosa PAO1 belongs to theHADsuperfamily and contains the motifs I, II and III, that are involved in phosphate moiety of the substrate and the Mg binding. With phosphorylcholine (Pch) or p-NPP as substrates, PchP is also activated by Zn2+ or Cu2+. To know the activation mechanism produced by these divalent cations we studied their effect with Pch. Saturation curves of recombinant PchP (expressed in E. coli) by different Pch concentrations against variable metal ion concentrations indicated that PchP contains two sites for Pch and two sites for the cation. The affinity of the enzyme for Pch was dependent on the quality of the metal ion. The K values for Pch in the presence of Zn2+ , Cu2+ or Mg2+ was 0.03 mM, 0.06 mM or 0.2 mM, respectively. The K values, ranged between 0.5 and 1.0 mM. Under assay conditions adapted for each metal ion, the K values for Zn2+ , Cu and Mg were 0.06 .M, 1.8 mM and 15 M, respectively. The K values for Zn2+, Cu2+ and Mg2+ were 10 mM, 20 mM and 1500 mM, respectively. High concentrations of these cations decreased the enzyme inhibition produced by high Pch concentrations. Therefore, the divalent cations besides to act as activators may also act as anti-inhibitors of PchP activity. These results led us to search for a new molecular model for PchP that involves more than the motifs I, II and III.