Oxygen, activated, reaction

Flavohydroquinone bound to apoproteins plays a very important role in flavo-protein-catalysis, either in the electron-transfer to substrates or other enzymes or in the oxygen activation reaction. The chemical reactivity of 1,5-dihydroflavin bound to apoproteins can differ drastically from that of free flavin. The reactivity is likely governed by factors such as the conformation of the bound flavohydroquinone and the ionization state (cf. below). 

Kovaleva EG, Lipscomb JD. Versatility of biological non-heme Fe(II) centers in oxygen activation reactions. Nat Chem Biol. 2008 4 186-93. 

Intermediates in oxygen activation reactions of diiron enzymes... 

Activation of molecular oxygen has often been proposed to explain the catalytic effect of certain transition-metal complexes in the oxidation of organic compounds, but in most cases critical examination has shown that the catalyst merely assists in the homolysis of hydroperoxides leading to the familiar radical-chain process. This mechanism is now proposed for the metal-phthalocyanine-catalysed autoxida-tion of cumene, originally considered to be an example of an oxygen activation reaction. i However, the controversy does not seem to be resolved as yet since a... 

A combination of spectroscopies including Mossbauer and resonance Raman were used to identify the presence of a diiron-oxo cluster with properties similar to those identified in ribonucleotide reductase (RB2) and methane monooxygenase (MMO). These enzymes all share the ability to break unactivated carbon-hydrogen bonds with a nonheme diiron cluster cofactor. Fatty acid desaturation and methane oxidation require a two-electron reduction of the diiron cluster to initiate the oxygen activation reaction. Identification of a diiron cluster in the desaturase allowed us to propose a consensus diiron-oxo binding motif consisting of two repeats of (D/E)EXXH. 

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