Rieske dioxygenase

Figure 13.21 Mononuclear non-haem iron enzymes from each of the five families in structures which are poised for attack by 02. (a) The extradiol-cleaving catechol dioxygenase, 2,3-dihydroxy-biphenyl 1,2-dioxygenase (b) the Rieske dioxygenase, naphthalene 1,2-dioxygenase (c) isopenicillin N-synthase (d) the ot-ketoglutarate dependent enzyme clavaminate synthase and (e) the pterin-dependent phenylalanine hydroxylase. (From Koehntop et al., 2005. With kind permission of Springer Science and Business Media.)...

For alkene dihydroxylations, heavy metal oxides such as 0s04 and Ru04 can be applied. They are efficient catalysts but their toxitity makes their use less desirable and there is a dear need for non-toxic metal catalysts. Nevertheless, only a few reports have focused on the use of iron catalysts for alkene dihydroxylations. All systems described so far try to model the naturally occurring Rieske dioxygenase, an enzyme responsible for the biodegradation of arenes via cis-dihydroxylation by soil baderia [66]. 

Que and coworkers also presented the first N,N,0-ligand to mimic the Rieske dioxygenase. It is the most reactive catalyst for ds-dihydroxylation found to date (Figure 3.7) [71]. 

Rieske dioxygenases also catalyze a number of oxidations such as benzyhc hydroxylation, desatnration, snlfoxidation, O- and N-dealkylation. This large range of oxidative transformations indicates that Rieske dioxygenases may even be more versatile than the cytochromes P450 (see Iron Heme Proteins, Mono- Dioxygenases). 

The Rieske dioxygenases (so-called because they contain a Rieske [2Fe—2S] cluster in addition to the mononuclear iron centre) catalyse cw-dihydroxylation of arene double bonds using NADH as the source of two electrons again, both dioxygen atoms are incorporated into the cA-diol product. 

The reaction of nonheme Fe complexes that are analogues of Rieske dioxygenase enzymes have been studied by the group of Que [234,235] (see Chapter 18). A possible mechanism has been suggested [241] (Fig. 1.31) for a bispidme ligand. An [Fe oOH] intermediate is formed initially, which undergoes 0-0 bond homolysis to form a ferryl [Fe =O] oxidant and HO. The oxidant was formed independently by reaction of the complex with lodosylbenzene as indicated by the appearance of an expected electronic transition in the near infrared of e = 400 M cm . This was able to epoxidize czs-cyclooctene in an Ar atmosphere. 

K. Chen, L. Que Jr., czs-Dlhydroxylation of olefins by a nonheme iron catalyst. A functional model for Rieske dioxygenases, Angew. Chem. Int. Ed. Engl. 38 (1999) 2227. 

Key Words Nonheme, Iron, Biomimetic, Bio-inspired, Cytochrome P450, Rieske dioxygenases. Hydrogen peroxide. Peroxide activation. Homogeneous catalysis, c/s-Dihydroxylation, Mechanism, Catalytic additives. Asymmetric... 

M. D. Wolfe, D. J. Altier, A. Stubna, C. V. Popescu, E. Miinck, J. D. Lipscomb, Benzoate 1, 2-dioxygenase from Pseudomonas putida Single turnover kinetics and regulation of a two-component Rieske dioxygenase. Biochemistry 41 (2002) 9611. 

Figure 19 Rieske dioxygenase-catalyzed arene c/5-dihydr-oxylation reaction...

There is thus far only one Rieske dioxygenase that is crystallographically characterized (Figure The... 

Arene dioxygenases, or Rieske dioxygenases (RDO), are enzymes that contain both a mononuclear, nonheme iron center as well as a Rieske-type, Fe2S2 cluster. They have a wide-ranging... 

Figure 30 Tetradentate ligands used in models for Rieske dioxygenases.

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