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Different Effects of Mg and Zn on the Two Sites for Alkylammonium Compounds in Pseudomonas aeruginosa Phosphorylcholine Phosphatase.

Otero LH, Beassoni PR, Boetsch C, Lisa AT, Domenech CE - Enzyme Res (2011)

Bottom Line: 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.

View Article: PubMed Central - PubMed

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.

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.

No MeSH data available.


Mechanism of PchP inhibition produced by T4MA. The data shown in Figure 2 were analyzed with the program DYNAFIT. In this scheme, (E*) represents the enzyme bound to the metal ion for simplicity. S: substrate, I: inhibitor, and P: product. In this scheme, kcat1 ≫ kcat2.
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sch2: Mechanism of PchP inhibition produced by T4MA. The data shown in Figure 2 were analyzed with the program DYNAFIT. In this scheme, (E*) represents the enzyme bound to the metal ion for simplicity. S: substrate, I: inhibitor, and P: product. In this scheme, kcat1 ≫ kcat2.

Mentions: Experiments performed with Mg2+ or Zn2+ indicate that Zn2+ produced enzyme activation at concentrations 1,000-fold lower than Mg2+, and Zn2+ prevented inhibition due to the entry of the second Pcho molecule much more effectively than Mg2+. The experimental data obtained with T4MA showed that in the presence of either metal ion, Mg2+ or Zn2+, the inhibition produced by T4MA followed a mixed-type inhibition mechanism with competitive and partial uncompetitive components (Scheme 2). This type of inhibition was obtained with p-NPP, which is a substrate without the alkylammonium moiety, and it is confirmatory that the enzyme contains two binding sites for alkylammonium ion: one site, which is indicated by the competitive component, may be the site for the alkylammonium moiety of the Pcho substrate, and the second site may be responsible for inhibition due to high substrate concentration, which was shown with Pcho.


Different Effects of Mg and Zn on the Two Sites for Alkylammonium Compounds in Pseudomonas aeruginosa Phosphorylcholine Phosphatase.

Otero LH, Beassoni PR, Boetsch C, Lisa AT, Domenech CE - Enzyme Res (2011)

Mechanism of PchP inhibition produced by T4MA. The data shown in Figure 2 were analyzed with the program DYNAFIT. In this scheme, (E*) represents the enzyme bound to the metal ion for simplicity. S: substrate, I: inhibitor, and P: product. In this scheme, kcat1 ≫ kcat2.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3102446&req=5

sch2: Mechanism of PchP inhibition produced by T4MA. The data shown in Figure 2 were analyzed with the program DYNAFIT. In this scheme, (E*) represents the enzyme bound to the metal ion for simplicity. S: substrate, I: inhibitor, and P: product. In this scheme, kcat1 ≫ kcat2.
Mentions: Experiments performed with Mg2+ or Zn2+ indicate that Zn2+ produced enzyme activation at concentrations 1,000-fold lower than Mg2+, and Zn2+ prevented inhibition due to the entry of the second Pcho molecule much more effectively than Mg2+. The experimental data obtained with T4MA showed that in the presence of either metal ion, Mg2+ or Zn2+, the inhibition produced by T4MA followed a mixed-type inhibition mechanism with competitive and partial uncompetitive components (Scheme 2). This type of inhibition was obtained with p-NPP, which is a substrate without the alkylammonium moiety, and it is confirmatory that the enzyme contains two binding sites for alkylammonium ion: one site, which is indicated by the competitive component, may be the site for the alkylammonium moiety of the Pcho substrate, and the second site may be responsible for inhibition due to high substrate concentration, which was shown with Pcho.

Bottom Line: 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.

View Article: PubMed Central - PubMed

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.

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.

No MeSH data available.