Inhibition of the catecholase activity of biomimetic dinuclear copper complexes by kojic acid |
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| Authors: | G Battaini E Monzani L Casella L Santagostini R Pagliarin |
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| Institution: | (1) Dipartimento di Chimica Generale, Università di Pavia Via Taramelli 12, 27100 Pavia, Italy Tel.: +39-0382-507331 Fax: +39-0382-528544 e-mail: bioinorg@unipv.it, IT;(2) Dipartimento C.I.M.A., Centro CNR, Università di Milano Via Venezian 21, 20133 Milano, Italy, IT;(3) Dipartimento di Chimica Organica e Industriale Università di Milano, Via Venezian 21, 20133 Milano, Italy, IT |
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| Abstract: | The inhibition of the catechol oxidase activity exhibited by three dinuclear copper(II) complexes, derived from different
diaminotetrabenzimidazole ligands, by kojic acid 5-hydroxy-2-(hydroxymethyl)-γ-pyrone] has been studied. The catalytic mechanism of the catecholase reaction proceeds in two steps and for both of these
inhibition by kojic acid is of competitive type. The inhibitor binds strongly to the dicopper(II) complex in the first step
and to the dicopper-dioxygen adduct in the second step, preventing in both cases the binding of the catechol substrate. Binding
studies of kojic acid to the dinuclear copper(II) complexes and a series of mononuclear analogs, carried out spectrophotometrically
and by NMR, enable us to propose that the inhibitor acts as a bridging ligand between the metal centers in the dicopper(II)
catalysts.
Received: 23 August 1999 / Accepted: 20 January 2000 |
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| Keywords: | Tyrosinase Catechol oxidase Kojic acid Inhibition kinetics Dinuclear copper complexes |
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