The deoxygenated form [Cu(I)Cu(I)] of molluscan hemocyanin exhibits a catalase-like activity. The initial Formation of the met-derivative [Cu(II)Cu(II)] is followed by reaction of a second molecule of hydrogen peroxide, leading to oxy-hemocyanin. Sodium azide, a ligand that is also able to coordinate to the binuclear cupric site of met-hemocyanin, shows competitive inhibition of the regeneration reaction by hydrogen peroxide. Therefore, in the presence of an excess of azide the reduction of met-hemocyanin by hydrogen peroxide is prevented and the met-hemocyanin azide complex becomes the main reaction product. After removal of excess reactants, the derivative obtained exhibits the characteristic features of met-hemocyanin. The preparation of this derivative by the present method requires a shorter time and is carried out under milder chemical conditions than those used in other methods previously reported in the literature. Furthermore, this new method is based on trapping of a reaction intermediate and not on the chemical modification of the protein after the labilization of the active site.

Isolation of the met-derivative intermediate in the catalase-like activity of deoxygenated Octopus vulgaris hemocyanin

BUBACCO, LUIGI;SALVATO, BENEDETTO;BELTRAMINI, MARIANO
1998

Abstract

The deoxygenated form [Cu(I)Cu(I)] of molluscan hemocyanin exhibits a catalase-like activity. The initial Formation of the met-derivative [Cu(II)Cu(II)] is followed by reaction of a second molecule of hydrogen peroxide, leading to oxy-hemocyanin. Sodium azide, a ligand that is also able to coordinate to the binuclear cupric site of met-hemocyanin, shows competitive inhibition of the regeneration reaction by hydrogen peroxide. Therefore, in the presence of an excess of azide the reduction of met-hemocyanin by hydrogen peroxide is prevented and the met-hemocyanin azide complex becomes the main reaction product. After removal of excess reactants, the derivative obtained exhibits the characteristic features of met-hemocyanin. The preparation of this derivative by the present method requires a shorter time and is carried out under milder chemical conditions than those used in other methods previously reported in the literature. Furthermore, this new method is based on trapping of a reaction intermediate and not on the chemical modification of the protein after the labilization of the active site.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11577/2460400
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