Difference Between Single Component Aromatic Flavoprotein Hydroxylase

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Single-component aromatic flavoprotein hydroxylase. Several single-component aromatic flavoprotein hydroxylases have been studied comprehensively such as p-hydroxybenzoate hydroxylase (8), phenol hydroxylase (9), 2-methyl-3-hydroxypyridine-5-carboxylic acid monooxygenase (10), salicylate hydroxylase (11), anthranilate hydroxylase (12), melilolate hydroxylase (13). Generally, the catalytic cycles of these enzymes follow the reaction shown in Scheme 3. The reaction is composed of two parts: the reductive half-reaction and the oxidative half-reaction. Scheme 3 shows the catalytic cycle of p-hydroxybenzoate hydroxylase, the most extensively studied enzymes of the class, and also represents a general model of reaction mechanism for other single-component …show more content…
Flavin reductases catalyze the reduction of flavin by NAD(P)H and have been thought to be the main supplier providing free reduced flavin for the oxygenase component (19, 20, 21). The flavin reductases have been classified into two classes (22) (Scheme 4): class I includes the reductases containing a tightly bound flavin as a cofactor and class II includes the reductases having no cofactor bound to the enzyme. In the reaction of class I enzymes, the enzyme-bound flavin is initially reduced by NAD(P)H and later transfer electrons to a free flavin substrate. In the reaction of class II reductase, the reduction of flavin requires that both substrates form a ternary complexe since there is no redox cofactor on the enzyme. The reduced flavin products from both types of reductases were found involved in oxygenation of aromatic compounds (20, 23, 24) in light-emitting reaction of bacterial luciferase (25, 26), in reduction of ribonucleotide reductase (27), in the release of iron from ferrisiderophore (28), and in the formation of superoxide radical …show more content…
Chlorophenol 4-monooxygenase was isolated from Burkholderia cepacia AC1100 catalyzes hydroxylation and de-chlorination of 2, 4, 6-trichlorophenol (30, 31). Hydroxylation of p-nitrophenol is carried out by the two-component monooxygenase in Bacillus sphaericus JS905 (32). Degradation of metal chelators such as oxidation of EDTA is carried out by the enzyme isolated from bacterial strains DSM9103 and BNC1 (33, 34) and enzyme isolated from Chelatobacter heintzii ATCC 29600 catalyzes degradation of nitrilotriacetic acid (35, 36). Alkanosulfonate monooxygenase catalyzes conversion of alkanosulfonate to aldehyde and sulfite (24, 37). Conversion of pyrrole-2-carboxylate is carried out by pyrrole-2-carboxylate monooxygenase from Rhodococcus sp. (38). Phenol hydroxylase from Bacillus thermoglucosidasius A7 catalyzes the hydroxylation of phenol compound (21, 39). Polyphenol oxygeanse is carried out by the enzymes in Pseudomonas pickettii DTP0602 and Ralstonia euthopha JMP134 (40, 41). To date, studies of these enzymes have been carried out at the stage of enzyme isolation or gene cloning and expression. None of these enzymes have been thoroughly investigated in mechanistic detail except for the studies of p-hydroxyphenylacetate hydroxylase from Pseudomonas putida (42, 43, 44). Kinetic studies of this enzyme have found that the

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