Abstract

Transition metal ions exhibit a unique role in diverse biological activities of proteins by acting as cofactors. In particular, zinc and copper ions modulate enzymes activities as well as many catalytic and oxidative/reductive processes. The kinetics and mechanism of the substitution reactions of dichloro [ZnCl2(terpy)] and [CuCl2(terpy)]  (terpy = 2,2′:6′,2′′-terpyridine) with biologically relevant ligands have been studied as a function of nucleophile concentrations at pH 7.38, under pseudo-first-order condition by UV-Vis spectrophotometric techniques. The interactions of Cu(II) and Zn(II) complexes with tripeptide glutathione (GSH) were investigated under pseudo-first-order conditions with respect to the complex concentration. For the substitution process of Zn(II) complex with glutathione (GSH), pre-equilibrium and chelate formation have been noted. The [CuCl2(terpy)] is more reactive than [ZnCl2(terpy)] complex and the second-order rate constants for the first step follow the order of reactivity: GSH > DL-Asp > L -Met > 5’-GMP ~ 5’-IMP for Cu(II)  complex,  while for Zn(II) the order of reactivity is: DL-Asp >  L -Met > GSH ~  5’-GMP > 5’-IMP. The results are discussed in terms of mechanisms of interactions between metalloproteins and biomolecules.

Highlights

  • Transition metal compounds play crucial role as a cofactor in metalloproteins [1]

  • Our aim of work is to investigate the mechanism of interaction between zinc(II) and copper(II) complexes and biomolecules in proteins environmental

  • The substitution reactions include two steps. Both steps are depending of the biomolecules concentration

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Summary

Introduction

Transition metal compounds play crucial role as a cofactor in metalloproteins [1]. They have unique role in diverse biological activities. Two essential metal ions zinc and copper have important role in enzyme activity, catalytic, regulatory function, oxidative-reductive processes and etc [1]. Biometal ions exist in single oxidation states such as zinc(II), which plays important role as a structural element in zinc-fingers, hydrolases, peptidases, anhydrases, in gene regulation, etc [1]. As a catalytic cofactor Cu(II) is required in metalloproteins, plays important role in biological oxidation-reduction reactions, in electron transfer, because exists in multiple oxidation states Cu(II)/Cu(I) [1].

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