Copper-Dioxygen Complexes. Inorganic and Bioinorganic Perspectives

Kitajima, Nobumasa; Moro‐oka, Yoshihiko

doi:10.1021/cr00027a010

Cited by 881 publications

(529 citation statements)

References 28 publications

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“…If two Cu centers are strongly exchange-coupled, the O 2 reaction with the reduced protein would lead to fast ET from both Cu sites to O 2 , generating a 2-e Ϫ reduced binuclear-or mononuclear-Cu II -peroxide level species (O 2 2Ϫ ), depending on the distance between the two Cu atoms (Table 1, rows A-E). These Cu II -peroxo͞hydroperoxo complexes do not appear to be reactive in Hatom abstraction (1,5,(30)(31)(32)(33)(34), nor is the mononuclear Cu M II -OOH species considered above (13,16). Although 4-e Ϫ reduction of O 2 by two Cu atoms could lead to a bis--oxo-Cu 2 III species (Table 1, row G), which is very reactive in H-atom abstraction, the existence of the Cu III oxidation state in a biological environment is not known and likely not accessible because of the inability of biological ligands (His, etc.)…”

Section: Correlation Of Electronicmentioning

confidence: 98%

O ₂ activation by binuclear Cu sites: Noncoupled versus exchange coupled reaction mechanisms

Chen

Solomon

2004

Proc. Natl. Acad. Sci. U.S.A.

161

146

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Binuclear Cu proteins play vital roles in O2 binding and activation in biology and can be classified into coupled and noncoupled binuclear sites based on the magnetic interaction between the two Cu centers. Coupled binuclear Cu proteins include hemocyanin, tyrosinase, and catechol oxidase. These proteins have two Cu centers strongly magnetically coupled through direct bridging ligands that provide a mechanism for the 2-electron reduction of O2 to a -2 : 2 side-on peroxide bridged Cu II 2 (O 2 2؊ ) species. This side-on bridged peroxo-Cu 2 II species is activated for electrophilic attack on the phenolic ring of substrates. Noncoupled binuclear Cu proteins include peptidylglycine ␣-hydroxylating monooxygenase and dopamine ␤-monooxygenase. These proteins have binuclear Cu active sites that are distant, that exhibit no exchange interaction, and that activate O2 at a single Cu center to generate a reactive Cu II ͞O2 species for H-atom abstraction from the C-H bond of substrates. O2 intermediates in the coupled binuclear Cu enzymes can be trapped and studied spectroscopically. Possible intermediates in noncoupled binuclear Cu proteins can be defined through correlation to mononuclear Cu II ͞O2 model complexes. The different intermediates in these two classes of binuclear Cu proteins exhibit different reactivities that correlate with their different electronic structures and exchange coupling interactions between the binuclear Cu centers. These studies provide insight into the role of exchange coupling between the Cu centers in their reaction mechanisms.

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Section: Correlation Of Electronicmentioning

confidence: 98%

O ₂ activation by binuclear Cu sites: Noncoupled versus exchange coupled reaction mechanisms

Chen

Solomon

2004

Proc. Natl. Acad. Sci. U.S.A.

161

146

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“…2 coordination, their biological functions are very different (1,2). Hemocyanins serve as oxygen carriers for many chelicerates and crustaceans (3)(4)(5).…”

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confidence: 99%

“…After limited proteolysis, the phenoloxidase so produced shows both a monophenoloxidase and an o-diphenoloxidase activity. Phenoloxidase is widespread in animals and plants as well as in fungi; it starts the synthesis of melanin, is involved in defense reactions (19 -20), and is also crucial for arthropod sclerotization, using N-acetyldopamine (NADA) 1 as substrate (21,22). Although much is known about the biological functions of phenoloxidase, its molecular mechanism and regulation are not well understood because of the lack of any known structure (2,13).…”

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confidence: 99%

Tarantula Hemocyanin Shows Phenoloxidase Activity

Decker

Rimke

1998

Journal of Biological Chemistry

205

139

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An enzyme generally catalyzes one well defined reaction with high specificity and efficiency. We report here in contrast that the copper protein hemocyanin of the tarantula Eurypelma californicum exhibits two different functions. These occur at the same active site. While hemocyanin usually is an oxygen carrier, its function can be transformed totally to monophenoloxidase and o-diphenoloxidase activity after limited proteolysis with trypsin or chymotrypsin. N-acetyldopamine (NADA) is more effectively oxidized than L-dopa or dopamine. This irreversible functional switch of tarantula hemocyanin function is limited to the two subunits b and c of its seven subunit types. A conserved phenylalanine in the hemocyanin molecule acts as a placeholder for other substrates that are phenylalanine derivatives. The proteolytic cleavage removes an N-terminal fragment, including the critical phenylalanine residue, which opens an entrance for substrates. Therefore no new arrangement of the active site, with its two copper atoms and the ؊ 2 : 2 bound O 2 molecule, is necessary to develop the catalytic function.

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“…The Cu 2 (μ-η 2 :η 2 -O 2 ) species has attracted attention in the model studies of type III copper proteins because this structure is suggested as an important motif in biological systems (Karlin and Tyeklár, 1993;Kitajima and Moro-oka, 1994). Although oxyhemocyanin (oxyHc) and oxytyrosinase (oxyTy) have this species in the active site, they show different functions: oxygen transport and oxygen activation, respectively (Cooksey et al, 1997;Cuff et al, 1998;Holm et al, 1996;Solomon et al, 1992).…”

Section: Introductionmentioning

confidence: 99%

Chemical Indices of the Biomimetic Models of Oxyhemocyanin and Oxytyrosinase

Takano¹,

Yamaguchi²,

Nakamura³

2011

Biomimetic Based Applications

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Copper-Dioxygen Complexes. Inorganic and Bioinorganic Perspectives

Cited by 881 publications

References 28 publications

O ₂ activation by binuclear Cu sites: Noncoupled versus exchange coupled reaction mechanisms

O ₂ activation by binuclear Cu sites: Noncoupled versus exchange coupled reaction mechanisms

Tarantula Hemocyanin Shows Phenoloxidase Activity

Chemical Indices of the Biomimetic Models of Oxyhemocyanin and Oxytyrosinase

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Copper-Dioxygen Complexes. Inorganic and Bioinorganic Perspectives

Cited by 881 publications

References 28 publications

O 2 activation by binuclear Cu sites: Noncoupled versus exchange coupled reaction mechanisms

O 2 activation by binuclear Cu sites: Noncoupled versus exchange coupled reaction mechanisms

Tarantula Hemocyanin Shows Phenoloxidase Activity

Chemical Indices of the Biomimetic Models of Oxyhemocyanin and Oxytyrosinase

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O ₂ activation by binuclear Cu sites: Noncoupled versus exchange coupled reaction mechanisms

O ₂ activation by binuclear Cu sites: Noncoupled versus exchange coupled reaction mechanisms