Oxygenases monooxygenases

Oxygenases - add one (monooxygenases) or both (dioxygenases) atoms of molecular oxygen to molecules, eg... 

Carotene cleavage enzymes — Two pathways have been described for P-carotene conversion to vitamin A (central and eccentric cleavage pathways) and reviewed recently. The major pathway is the central cleavage catalyzed by a cytosolic enzyme, p-carotene 15,15-oxygenase (BCO EC 1.13.1.21 or EC 1.14.99.36), which cleaves p-carotene at its central double bond (15,15 ) to form retinal. Two enzymatic mechanisms have been proposed (1) a dioxygenase reaction (EC 1.13.11.21) that requires O2 and yields a dioxetane as an intermediate and (2) a monooxygenase reaction (EC 1.14.99.36) that requires two oxygen atoms from two different sources (O2 and H2O) and yields an epoxide as an intermediate. ... 

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

Locher HH, T Leisinger, AM Cook (1991b) 4-Toluene sulfonate methyl monooxygenase from Comamonas testosteroni T-2 purification and some properties of the oxygenase component. J Bacteriol 173 3741-3748. 

The alkane hydroxylase belongs to a family of nonheme iron oxygenases. There is some structural similarity between the nucleotide sequence of the integral-membrane alkane hydroxylase and the subunits of the monooxygenase encoded by xylA and xylM in the TOL plasmid that are involved in hydrox-ylation of the methyl groups in toluene and xylene in Pseudomonas putida PaWl (Suzuki et al. 1991). 

Rosche, B. Tshisuaka, B. Hauer, B., et al., 2-Oxo-l,2-Dihydroquinoline 8-Monooxygenase, Phylogenetic Relationship to other Multicomponent Nonheme Iron Oxygenases. J. Bacteriol, 1997. 179(11) pp. 3549-54. 

The systems where this type of reaction is produced may be metal-, heme- or flavin-dependent. In flavin-dependent monooxygenases, a flavin-oxygen intermediate reacts with the substrate, producing water in a second step and requiring cofactors for regeneration of the flavin moiety. The non-heme-dependent oxygenases include the... 

The first step is catalysed by the tetrahydrobiopterin-dependent enzyme tyrosine hydroxylase (tyrosine 3-monooxygenase), which is regulated by end-product feedback is the rate controlling step in this pathway. A second hydroxylation reaction, that of dopamine to noradrenaline (norepinephrine) (dopamine [3 oxygenase) requires ascorbate (vitamin C). The final reaction is the conversion of noradrenaline (norepinephrine) to adrenaline (epinephrine). This is a methylation step catalysed by phenylethanolamine-jV-methyl transferase (PNMT) in which S-adenosylmethionine (SAM) acts as the methyl group donor. Contrast this with catechol-O-methyl transferase (COMT) which takes part in catecholamine degradation (Section 4.6). 

The following is review on the molecular and physical properties of this class of monooxygenases, which are also known as hydroxylases. A typical monooxygenase reaction is the hydroxylation of an alkane to an alcohol which involves a reduced cosubstrate that reduces a second atom within the O2 molecule to form water. Flavin-containing monooxygenases include lysine oxygenase and 4-hydroxybenzoate hydroxylase. Reduced pteri-dines are involved in the phenylalanine hydroxylase and tryptophan hydroxylase reactions. See also Cytochrome P-450... 

IMIDAZOLEACETATE HYDROXYLASE INDOLEAMINE 2,3-DIOXYGENASE myo-INOSITOL OXYGENASE JUGLONE MONOOXYGENASE KYNURENINE 3-HYDROXYLASE LACCASE... 

The monooxygenase group of enzymes includes the non-P450 hydroxylases which catalyze the insertion of a hydroxyl group to replace a hydrogen atom at a saturated carbon [6-8] and the non-heme-dependent oxygenases such as the flavin-molybdenum-cobalt-dependent xanthine oxidase and aldehyde oxidase... 

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