A class III peroxidase, isolated and characterized from the latex of the perennial Mediterranean shrub Euphorbia characias, contains one ferric iron-protoporphyrin IX pentacoordinated with a histidine 'proximal' ligand as heme prosthetic group. In addition, the purified peroxidase contained 1 mole of endogenous Ca(2+) per mole of enzyme, and in the presence of excess Ca(2+), the catalytic efficiency was enhanced by three orders of magnitude. The incubation of the native enzyme with Ni(2+) causes reversible inhibition, whereas, in the presence of excess Ca(2+), Ni(2+) leads to an increase of the catalytic activity of Euphorbia peroxidase. UV/visible absorption spectra show that the heme iron remains in a quantum mechanically mixed-spin state as in the native enzyme after addition of Ni(2+), and only minor changes in the secondary or tertiary structure of the protein could be detected by fluorescence or CD measurements in the presence of Ni(2+). In the presence of H(2)O(2) and in the absence of a reducing agent, Ni(2+) decreases the catalase-like activity of Euphorbia peroxidase and accelerates another pathway in which the inactive stable species accumulates with a shoulder at 619 nm. Analysis of the kinetic measurements suggests that Ni(2+) affects the H(2)O(2)-binding site and inhibits the formation of compound I. In the presence of excess Ca(2+), Ni(2+) accelerates the reduction of compound I to the native enzyme. The reported results are compatible with the hypothesis that ELP has two Ni(2+)-binding sites with opposite functional effects.

ALLOSTERIC MODULATION OF EUPHORBIA PEROXIDASE BY NICKEL IONS / Pintus, F; Mura, A; Bellelli, Andrea; Arcovito, Alessandro; Spanò, D; Pintus, A; Floris, G; Medda, R.. - In: THE FEBS JOURNAL. - ISSN 1742-464X. - STAMPA. - 275:(2008), pp. 1201-1212. [10.1111/j.1742-4658.2008.06280.x]

ALLOSTERIC MODULATION OF EUPHORBIA PEROXIDASE BY NICKEL IONS.

BELLELLI, Andrea;ARCOVITO, Alessandro;
2008

Abstract

A class III peroxidase, isolated and characterized from the latex of the perennial Mediterranean shrub Euphorbia characias, contains one ferric iron-protoporphyrin IX pentacoordinated with a histidine 'proximal' ligand as heme prosthetic group. In addition, the purified peroxidase contained 1 mole of endogenous Ca(2+) per mole of enzyme, and in the presence of excess Ca(2+), the catalytic efficiency was enhanced by three orders of magnitude. The incubation of the native enzyme with Ni(2+) causes reversible inhibition, whereas, in the presence of excess Ca(2+), Ni(2+) leads to an increase of the catalytic activity of Euphorbia peroxidase. UV/visible absorption spectra show that the heme iron remains in a quantum mechanically mixed-spin state as in the native enzyme after addition of Ni(2+), and only minor changes in the secondary or tertiary structure of the protein could be detected by fluorescence or CD measurements in the presence of Ni(2+). In the presence of H(2)O(2) and in the absence of a reducing agent, Ni(2+) decreases the catalase-like activity of Euphorbia peroxidase and accelerates another pathway in which the inactive stable species accumulates with a shoulder at 619 nm. Analysis of the kinetic measurements suggests that Ni(2+) affects the H(2)O(2)-binding site and inhibits the formation of compound I. In the presence of excess Ca(2+), Ni(2+) accelerates the reduction of compound I to the native enzyme. The reported results are compatible with the hypothesis that ELP has two Ni(2+)-binding sites with opposite functional effects.
heme peroxidase; euphorbia characias; allosteric regulation
01 Pubblicazione su rivista::01a Articolo in rivista
ALLOSTERIC MODULATION OF EUPHORBIA PEROXIDASE BY NICKEL IONS / Pintus, F; Mura, A; Bellelli, Andrea; Arcovito, Alessandro; Spanò, D; Pintus, A; Floris, G; Medda, R.. - In: THE FEBS JOURNAL. - ISSN 1742-464X. - STAMPA. - 275:(2008), pp. 1201-1212. [10.1111/j.1742-4658.2008.06280.x]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/105531
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