Bacterial monooxygenase

The mechanism of hydroxylation by the bacterial monooxygenase has been resolved to show four main steps in the sequence of cytochrome P-450 reactions (Fig. 1). 

Bacterial monooxygenases that are flavoproteins requiring NADPH are involved in the hydroxylation of a number of phenolic compounds (a) phenol and chlorophenols, (b) salicylate, (c) 4-hydroxybenzoate, (d) 4-hydroxyphenylacetate, and (e) anthranilate in fungi. Further details of some of these are given later in this chapter and in Chapter 6 (Sections 6.2.1 and 6.5.1.2). 

Both electron transfer chains cannot substitute each other in reconstituted systems, which points to a different phylogenetic origin of mitochondrial and bacterial monooxygenases on the one hand and the microsomal enzymes on the other. Microsomes also contain cytochrome bs which is able to donate electrons to the monooxygenases. However, the physiological role of this cytochrome is still controversial and more than one function has to be considered. 

Another type of iron-containing monpoxygenase was flrst described by Bernhardt et al. ) and contains a two iron-two-acid-labile-sulfur cluster. It was isolated from bacteria and catalyzes the 0-demethylation of 4-methoxybenzoate The corresponding electron transport chain involves NADH, a flavoprotein and a second iron-sulfur protein It seems that many more bacterial monooxygenases belong to this type rather than to the heme-sulfur-containing category. 

Organic chemists often use enantiomencally homogeneous starting materials for the synthe SIS of complex molecules (see Chiral Drugs p 296) A novel preparation of the S enantiomer of compound B has been descnbed using a bacterial cyclohexanone monooxygenase enzyme system... 

Enantioselective oxidation of cyclic dithioacetals to monosulfoxides catalyzed by bacterial cyclohexanone monooxygenases 96CC2303. 

Wieser M, B Wagner, J Eberspacher, F Lingens (1997) Puriflcation and characterization of 2,4,6-trichloro-phenol-4-monooxygenase, a dehalogenating enzyme imm Azotobacter sp. strain GPL J Bacterial 179 202-208. 

Eppink MHM, SA Boeren, J Vervoort, WJH van Berkel (1997) Purification and properties of 4-hydroxybenzoate 1-hydroxylase (decarboxylating), a novel flavin adenine dinucleotide-dependent monooxygenase from Candida parapsilosis CBS604. J Bacterial 179 668-6687. 

Fukumori F, RP Hausinger (1993a) Alcaligenes eutrophus JMP 134 2,4-chlorophenoxyacetate monooxygenase is an a-ketoglutarate-dependent dioxygenase. J Bacterial 175 2083-2086. 

Xun L (1996) Purification and characterization of chlorophenol 4-monooxygenase from Burkholderia cepacia ACnOO. J Bacterial 178 2645-2649. 

Zahn JA, AA DiSpirito (1996) Membrane associated methane monooxygenase from Methylococcus capsula-tus (Bath). J Bacterial 178 1018-1029. 

Whited GM, DT Gibson (1991) Separation and partial characterization of the enzymes of the toluene-4-monooxygenase catabolic pathway in Pseudomonas mendocina KRl. J Bacterial 173 3017-3020. 

A number of bacterial strains with monooxygenase activity have been described, and different types of MMO have played important roles in the degradation of a range of aliphatic componnds. MMO may exist in either a soluble (sMMO) form that has been more extensively studied or in a particulate (pMMO) form. These forms display different substrate ranges and different rates of transformation rates, and most methanotrophs express only the particnlate form of the enzyme (Hanson and Hanson 1996). 

Payne JW, H Bolton, JA Campbell, L Xun (1998) Purification and characterization of EDTA monooxygenase from the EDTA-degrading bacterium BNCl. J Bacterial 180 3823-3827. 

Small FJ, SA Ensign (1997) Alkene monooxygenase from Xanthobacter strain Py2. Purification and characterization of a four-component system central to the bacterial metabolism of aliphatic alkenes. J Biol Chem 272 24913-24920. 

Hartmans S, MJ van der Werf, JAM de Bont (1990) Bacterial degradation of styrene involving a novel flavin adenenine dinucleotide-dependent styrene monooxygenase. Appl Environ Microbiol 41 1045-1054. 

Zhou N-Y, J Al-Dulayymi, MS Baird, PA Williams (2002) Salicylate 5-hydroxylase from Ralstonia sp. strain U2 a monooxygenase with close relationships to and shared electron transport proteins with naphthalene dioxygenase. J Bacterial 184 1547-1555. 

Martin G, S Dijols, C Capeillere-Blandin, 1 Arnaud (1999) Hydroxylation reaction catalyzed by the Burk-holderia cepacia ACllOO bacterial strain. Involvement of the chlorophenol-4-monooxygenase. Eur J Bioichem 261 533-538. 

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