Dioxygen activation by enzymes containing binuclear non-heme iron clusters
Article Abstract:
Binuclear non-heme iron clusters, methane monooxygenase (MMO) and the small subunit of ribonucleotide reductase (R2), activate dioxygen to stabilizes all the redox states between Fe(II)-Fe(II) and Fe(IV)-Fe(IV). The presence of two adjacent sites for exogenous ligands on the two Fe of MMO and R2 suggest that dioxygen activation involves a bridging complex. The initial bond breakage is homolytic, which gives the oxo-Fe(super IV)Fe(super IV) state that is equivalent to P450-pi-cation radical reactive species. This facilitates the forward reaction and yields the more reactive heterolytic cleavage product.
Publication Name: Chemical Reviews
Subject: Chemistry
ISSN: 0009-2665
Year: 1996
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Dioxygen activation by enzymes with mononuclear non-heme iron active sites
Article Abstract:
Enzymes with mononuclear non-heme iron (Fe) active sites use the Lewis acidic character of their Fe(III) centers to stimulate the reaction of substrates with dioxygen. The Fe center binds dioxygen after the reduction of dioxygen to a peroxide level. The Fe(II) enzymes bind with O2 directly. The active sites have at least one coordination site that is vacant or occupied by water. Thus, it is available for the binding of ligands such as a substrate, cofactor or O2. This variability in the coordination differentiates the non-heme iron sites from those in heme enzymes.
Publication Name: Chemical Reviews
Subject: Chemistry
ISSN: 0009-2665
Year: 1996
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Manganese cluster in photosynthesis: where plants oxidize water to dioxygen
Article Abstract:
The tetranuclear manganese complex in the oxygen-evolving complex of the photosystem II catalyzes the oxidation of water to dioxygen. The variable oxidation states of manganese enable it to participate in this redox reaction. The photosystem II possesses four Mn atoms, six polypeptides and one smaller polypeptide. Calcium and chloride ions are needed for maximal oxygen formation. The mechanism involves the incorporation of two water molecules as hydroxide bridges during the S4 to S0 transition when dioxygen is released.
Publication Name: Chemical Reviews
Subject: Chemistry
ISSN: 0009-2665
Year: 1996
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