Copper hydroperoxo intermediate

Recently, great progress has been made in the clarification of the reaction mechanism of DpM. The formation of a copper hydroperoxo intermediate has been suggested by Klinman et al. as shown in Scheme 11 [183]. Requirement of proton uptake prior to substrate hydroxylation has been indicated from the results on the pH-dependent isotope effects, suggesting the formation of the copper hydroperoxo intermediate [183]. A generation of the benzylic radical from the substrate in the catalytic cycle has been postulated from the experiments using inhibitors [206, 207]. While the copper hydroperoxo intermediate is a possible candidate as an active intermediate which is... 

Hydroperoxo, alkylperoxo, and acylperoxo copper(II) complexes While there is no direct experimental indication of involvement of dinuclear hydroperoxo copper(II) intermediate in the catalysis of tyrosinase, a dinuclear hydroperoxo copper(II) complex and related alkyl and acylperoxo complexes have been prepared either by reaction of a dinuclear jii-hydroxo complex [Cu2 (XYL-0 )(0H)] with XOOH (X=H, R, RCO) or by treating a peroxo complex [Cu2(XYL-0 )(02)] with X [138-140]. The acylperoxo complex was isolated and its molecular structure was established by X-ray crystallography (see Fig. 10). 

Transition metal hydroperoxo species are well established as important intermediates in the oxidation of hydrocarbons (8,70,71). As they relate to the active oxygenating reagent in cytochrome P-450 monooxygenase, (porphyrin)M-OOR complexes have come under recent scmtiny because of their importance in the process of (poiphyrin)M=0 formation via 0-0 cleavage processes (72-74). In copper biochemistry, a hydroperoxo copper species has been hypothesized as an important intermediate in the catalytic reaction of the copper monooxygenase, dopamine P-hydroxylase (75,76). A Cu-OOH moiety has also been proposed to be involved in the disproportionation of superoxide mediated by the copper-zinc superoxide dismutase (77-78). Thus, model Cun-OOR complexes may be of... 

In light of the accepted mechanism for cytochrome P-450 (97-100), a superoxo-Cu(II) intermediate is further reduced, leading to dioxygen activation. Accordingly, a monomeric peroxo or hydroperoxo copper(II) complex serves as a synthetic model for these intermediates of copper-containing monooxygenases. However, no well-characterized complexes of these types are available to date. Formation of a monomeric hydroperoxo or acylperoxo complex was reported to occur when a trans-/u-l,2-peroxo complex, [(Cu(TPA))2(02)]z+, was treated with H+ or RC(O)+, but no details of the structures and properties of the complexes were provided (101). A related complex, a monomeric acylperoxo cop-per(II) complex, was synthesized (102). Low-temperature reaction of a dimeric copper(II) hydroxide complex, [Cu(HB(3,5-iPr2pz)3)]2(OH)2, with 2 equivalents of m-CPBA (3-chloroperoxybenzoic acid) yielded a monomeric acylperoxo complex whose structure was characterized by... 

It can be a Cu -hydroperoxo species formed as in Eq. (17) of Fig. 13. A homolysis of the 0-0 bound could allow the abstraction of a hydrogen atom from DNA that gives rise to a DNA radical and a new copper complex (Cu -0 or its canonical form Cu =0), Eq. (18). This last intermediate may... 

The catalytic mechanism of GOase has been extensively studied (Fig. 8) 63,64). The primary alcohol first coordinates to the active species A, leading to the formation of the metal-phenoxyl radical complex B. This species undergoes proton abstraction from the substrate by the axial tyrosinate (Tyr495), followed by a rapid intramolecular electron transfer from the intermediate ketyl radical anion with reduction of Cu to Cul The copper(I) species C reacts with dioxygen to form the hydroperoxo copper(II) complex D with the liberation of the aldehyde. Finally, dihydrogen peroxide is released to give back the active form of the enzyme. 

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