Monooxygenase dioxygen

Toluene monooxygenases provide alternatives to dioxygenation, and the ortho-mono-oxygenase in Burkholderia (Pseudomonas) cepacia G4 has been shown to be carried... 

Dioxygenation may result in the elimination of nitrite in reactions that are analogous to the elimination of sulfite from aromatic sulfonates, or halogen from 2-halobenzoates. As an alternative to dioxygenation, toluene-3- and toluene-4-monooxygenases can transform nitrobenzene to 4- or 3-nitrophenol, with the former dominating (Fishman et al. 2004) ... 

Figure 14.4 The dioxygen site in peptidylglycine a-hydroxylating monooxygenase incubated in the presence of IYT. (From Bento et al., 2006. With kind permission of Springer Science and Business Media.)...

The irreversible coordination of dioxygen to metal complexes is of remarkable importance in order to explain the activity of enzymes such monooxygenases, dioxygenases and cytochrome c oxidase. 

Monooxygenases, by incorporation of a single atom of dioxygen in reactions of the type ... 

Tyrosinase is a monooxygenase which catalyzes the incorporation of one oxygen atom from dioxygen into phenols and further oxidizes the catechols formed to o-quinones (oxidase action). A comparison of spectral (EPR, electronic absorption, CD, and resonance Raman) properties of oxy-tyrosinase and its derivatives with those of oxy-Hc establishes a close similarity of the active site structures in these proteins (26-29). Thus, it seems likely that there is a close relationship between the binding of dioxygen and the ability to "activate" it for reaction and incoiporation into organic substrates. Other important copper monooxygenases which are however of lesser relevance to the model studies discussed below include dopamine p-hydroxylase (16,30) and a recently described copper-dependent phenylalanine hydroxylase (31). 

As suggested above, we can speculate that the biological relevance of the observations described above pertain to the activation of dioxygen in copper monooxygenases via protonation of a peroxo-Cun (derived from Cu(I) and O2)... 

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