Flavin-containing dioxygenases

A wide range of soluble redox enzymes contain one or more intrinsic [2Fe-2S]2+ +, [3Fe-4S]+ , or [4Fe S]2+ + clusters that function in electron transport chains to transfer electrons to or from nonheme Fe, Moco/Wco, corrinoid, flavin, thiamine pyrophosphate (TPP), Fe S cluster containing, or NiFe active sites. Many have been structurally and spectroscopically characterized and only a few of the most recent examples of each type are summarized here. Dioxygenases that function in the dihydroxylation of aromatics such as benzene, toluene, benzoate, naphthalene, and phthalate contain a Rieske-type [2Fe-2S] + + cluster that serves as the immediate electron donor to the monomeric nonheme Fe active site see Iron Proteins with Mononuclear Active Sites). The xanthine oxidase family of molybdoenzymes see Molybdenum MPT-containing Enzymes) contain two [2Fe-2S] + + clusters that mediate electron transfer between the Moco active site and the Other soluble molybdoen-... 

A bacterial flavohemoglobin, which contains a globin domain fused to a flavin/NADH binding domain, functions enzymatically as a nitric oxide dioxygenase, using a catalytic cycle similar to that in Figure 10. The role of this enzyme is apparently to detoxify nitric oxide produced by the body in response to bacterial infection. The distal pocket of flavohemoglobins more closely... 

One of the two important parts of enzyme is a flavo-iron-sulfur protein with NADH-dependent oxidoreductase activity. The reductase is a monomeric 34 kDa (in case of phthalate dioxygenase reductase) flavo-iron-sulfur protein containing flavin mononucleotide (FMN) and a plant-ferredoxin-type [2Fe-2S] center in a 1 1 ratio [372]. Structure of this part of the enzyme has been studied recently by X-ray crystallographic analysis [375], low-temperature EPR [383], and kinetically [378]. 

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