Solution chemical properties and catecholase-like activity of the copper(ii)–Ac-His-His-Gly-His-OH system, a relevant functional model for copper containing oxidases

Abstract

The solution chemical properties, superoxide dismutase and catecholase activity of the copper(ii)-Ac-His-His-Gly-His-OH (hhgh) complexes were studied to identify functional and structural models of copper-containing oxidases. The solution speciation was determined in the pH range 3-11 by two independent methods (potentiometry and pH-dependent EPR measurements). The results obtained by the two methods agree very well with each other and show the formation of differently protonated CuH(x)L complexes (where x= 2 ,1, 0, -1, -2, -3) in aqueous solution. The spectroscopic (UV-Vis, CD, EPR) data indicate that the coordination of the imidazole rings is a determinant factor in all these complexes. Amide coordinated complexes are dominant only above pH 8. This offers excellent possibilities for structural/functional modelling of copper(ii) containing metalloenzymes. Indeed, the {3N(im)} coordinated CuL species (pH = 6-7) has efficient superoxide dismutase-like activity. The {3N(im),OH(-)} coordinated CuH(-1)L possesses outstanding activity to catalyze the oxidation of 3,5-di-tert-butylcatechol (H(2)dtbc) by dioxygen in 86 wt% methanol-water, providing the first example that copper(ii)-peptide complexes are able to mimic copper containing oxidases.

Coordination characteristics of di-O-picolyl derivative of 1,1′-methylene-bis(2-naphthol): First crystal structure of a monomeric Cu(II) complex of bis{2-[(pyridin-2-yl)methoxy] naphthalen-1-yl}methane

“…The TON value observed in the present case is well within the range observed by a number of mono-and dinuclear copper complexes reported in the literature [8][9][10][11][12][13][14][15][16][17][18][19].…”

A minimalist chemical model of matrix metalloproteinases — Can small peptides mimic the more rigid metal binding sites of proteins?

“…As a consequence of the positively charged N-and C-terminal lysine residues, precipitate formation, which is very frequent in presence of zinc(II) and Nprotected peptides [29,30], was not observed. Around pH 7 the diprotonated complex ZnH 2 L is dominant in the solution (Figure 1).…”

Polidentát tripodális ligandumok biomimetikus fémkomplexei

“…[9][10][11][12][13][14] Az enzimek funkcionális modellezésére a peptid komplexek kézenfekvõ választásnak tûnnek, hiszen elvileg az aktív centrumhoz nagyon hasonló fémion környezet alakítható ki. Ennek ellenére a SOD enzim kivételével 10 kevés példa akad az irodalomban enzim mimetikus vizsgálatokra.…”

“…Ennek ellenére a SOD enzim kivételével 10 kevés példa akad az irodalomban enzim mimetikus vizsgálatokra. 9 Ennek oka nagyrészt az, hogy a kisméretû lineáris peptidekkel a fehérjék harmadlagos szerkezete által meghatározott aktív centrumhoz 123. évfolyam, 2. szám, 2017. hasonló környezet nem, vagy csak speciális esetekben alakítható ki. Bár néhány általunk vizsgált metallopeptid említésre méltó aktivitással bírt, 9,10 mindegyiknél gond volt a preorganizált szerkezet hiánya.…”