Transition from octahedral to tetrahedral geometry causes the activation or inhibition by Znf2+ of Pseudomonas aeruginosa phosphorylcholine phosphatase.
Pseudomonas aeruginosa phosphorylcholine phosphatase (PchP) catalyzes the hydrolysis of phosphorylcholine, which is produced by the action of hemolytic phospholipase C on phosphatidylcholine or sphyngomielin, to generate choline and inorganic phosphate. Among divalent cations, its activity is dependent on Mg(2+) or Zn(2+). Mg(2+) produced identical activation at pH 5.0 and 7.4, but Zn(2+) was an activator at pH 5.0 and became an inhibitor at pH 7.4. At this higher pH, very low concentrations of Zn(2+) inhibited enzymatic activity even in the presence of saturating Mg(2+) concentrations. Considering experimental and theoretical physicochemical calculations performed by different authors, we conclude that at pH 5.0, Mg(2+) and Zn(2+) are hexacoordinated in an octahedral arrangement in the PchP active site. At pH 7.4, Mg(2+) conserves the octahedral coordination maintaining enzymatic activity. The inhibition produced by Zn(2+) at 7.4 is interpreted as a change from octahedral to tetrahedral coordination geometry which is produced by hydrolysis of the [Zn(2+)L(2)(-1)L(2)(0) (H(2)O)(2)] complex.
Departamento de Biología Molecular, Universidad Nacional de Río Cuarto, 5800 Río Cuarto, Córdoba, Argentina.
Lisandro H
LH
Otero
Paola R
PR
Beassoni
Angela T
AT
Lisa
Carlos E
CE
Domenech
D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020134:Catalytic Domain; D006867:Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D010767:Phosphorylcholine / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000201:enzymology*; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism
D001426:Bacterial Proteins; D010767:Phosphorylcholine; D006867:Hydrolases; C404902:phosphorylcholine hydrolase; D015032:Zinc