This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Degradation/Utilization/Assimilation → Degradation/Utilization/Assimilation - Other|
Some taxa known to possess this pathway include : Fusarium oxysporum
Expected Taxonomic Range: Fungi
Many nitroalkane compounds are used in the chemical industry as intermediate compounds in chemical syntheses. Some of them are toxic or carcinogenic and their biodegradation is of considerable interest. Nitroalkane compounds are also biosynthesized by microorganisms and plants as defense chemicals (in [Kido75, Ha06]). Bacteria, yeasts, fungi and higher plants have been shown to oxidize nitroalkane compounds to their corresponding aldehydes or ketones, and nitrite. Industrially, oxidation of nitroalkanes to less toxic species can be used in bioremediation. Biologically, these oxidations can counter the production of toxic nitroalkanes by other organisms, or protect the producing organism [Nagpal06].
A nitroalkane degrading enzyme, nitroalkane oxidase, from the fungus Fusarium oxysporum, has been extensively studied and its crystal structure has been determined [Nagpal06]. This FAD-containing flavoprotein catalyzes the oxidation of primary nitroalkanes to aldehydes, and secondary nitroalkanes to ketones, along with the production of nitrite. Primary nitroalkanes are the best substrates. Its action on nitroethane is shown in this pathway. In contrast to other nitroalkane oxidizing enzymes (see below), this enzyme acts on neutral nitroalkanes rather than nitroalkanes in their anionic (nitronate) form (such as ethylnitronate), and electrons are transferred to oxygen to form hydrogen peroxide (in [Gadda00]). The physiological relevance of this enzyme is suggested by its induction upon growth of the organism in media containing nitroethane, and its use of neutral rather than anionic nitroalkanes as substrates. This also suggests that nitroethane is a physiological substrate [Kido78], in [Heasley96] and reviewed in [Fitzpatrick05].
Further catabolism of the acetaldehyde product in this organism has not been reported, although it may be metabolized by NADPH-aldehyde reductase/NADP-alcohol dehydrogenase. This enzyme reduces carbonyl compounds to the corresponding alcohols in fungi, yeasts and animals (in [Panagiotou04]). Nitrite may reduced to ammonia by nitrite reductase and used in nitrogen-containing biomolecules [Kido75]. These are indicated by the reaction links.
Another nitroalkane degrading enzyme, nitronate monooxygenase EC 22.214.171.124 (formerly 2-nitropropane dioxygenase EC 126.96.36.199), has been studied in the fungus Neurospora crassa [Gorlatova98, Francis05] and the yeast Cyberlindnera mrakii (previosuly known as Hansenula mrakii) [Kido76, Tchorzewski94]. Recombinant nitronate monooxygenase (formerly 2-nitropropane dioxygenase) from Pseudomonas aeruginosa has also been produced and its crystal structure determined [Ha06]. Nitronate monooxygenase oxidizes ethylnitronate to acetaldehyde and nitrite (see MetaCyc pathway alkylnitronates degradation). However, this enzyme differs from nitroalkane oxidase in its mechanism, its preference for the anionic form of the substrate, and it does not produce hydrogen peroxide as a product (reviewed in [Fitzpatrick05]).
Several other flavoenzymes from microorganisms have been shown to oxidize nitroalkanes including: nitroalkane dioxygenase from Streptomyces ansochromogenes [Zhang02b]; 3-nitropropionate oxidase (EC 188.8.131.52) from Penicillium atrovenetum [Porter87]; and glucose oxidase from Aspergillus niger [Porter77]. In mammals, nitroethane oxidation by D-amino acid oxidase from pig kidney has been shown [Porter73]. Unlike nitroalkane oxidase, these enzymes also react with the anionic form of the nitro-containing substrate.
Fitzpatrick05: Fitzpatrick PF, Orville AM, Nagpal A, Valley MP (2005). "Nitroalkane oxidase, a carbanion-forming flavoprotein homologous to acyl-CoA dehydrogenase." Arch Biochem Biophys 433(1);157-65. PMID: 15581574
Francis05: Francis K, Russell B, Gadda G (2005). "Involvement of a flavosemiquinone in the enzymatic oxidation of nitroalkanes catalyzed by 2-nitropropane dioxygenase." J Biol Chem 280(7);5195-204. PMID: 15582992
Gorlatova98: Gorlatova N, Tchorzewski M, Kurihara T, Soda K, Esaki N (1998). "Purification, characterization, and mechanism of a flavin mononucleotide-dependent 2-nitropropane dioxygenase from Neurospora crassa." Appl Environ Microbiol 1998;64(3);1029-33. PMID: 9501443
Ha06: Ha JY, Min JY, Lee SK, Kim HS, Kim do J, Kim KH, Lee HH, Kim HK, Yoon HJ, Suh SW (2006). "Crystal structure of 2-nitropropane dioxygenase complexed with FMN and substrate. Identification of the catalytic base." J Biol Chem 281(27);18660-7. PMID: 16682407
Kido76: Kido T, Soda K, Suzuki T, Asada K (1976). "A new oxygenase, 2-nitropropane dioxygenase of Hansenula mrakii. Enzymologic and spectrophotometric properties." J Biol Chem 251(22);6994-7000. PMID: 11214
Nagpal06: Nagpal A, Valley MP, Fitzpatrick PF, Orville AM (2006). "Crystal structures of nitroalkane oxidase: insights into the reaction mechanism from a covalent complex of the flavoenzyme trapped during turnover." Biochemistry 45(4);1138-50. PMID: 16430210
Porter73: Porter DJ, Voet JG, Bright HJ (1973). "Direct evidence for carbanions and covalent N 5 -flavin-carbanion adducts as catalytic intermediates in the oxidation of nitroethane by D-amino acid oxidase." J Biol Chem 248(12);4400-16. PMID: 4145800
Porter87: Porter DJ, Bright HJ (1987). "Propionate-3-nitronate oxidase from Penicillium atrovenetum is a flavoprotein which initiates the autoxidation of its substrate by O2." J Biol Chem 262(30);14428-34. PMID: 3667582
Zhang02b: Zhang J, Tan H (2002). "Cloning, expression and characterization of a gene encoding nitroalkane-oxidizing enzyme from Streptomyces ansochromogenes." Eur J Biochem 269(24);6302-7. PMID: 12473127
Daubner02: Daubner SC, Gadda G, Valley MP, Fitzpatrick PF (2002). "Cloning of nitroalkane oxidase from Fusarium oxysporum identifies a new member of the acyl-CoA dehydrogenase superfamily." Proc Natl Acad Sci U S A 99(5);2702-7. PMID: 11867731
Gadda97: Gadda G, Edmondson RD, Russell DH, Fitzpatrick PF (1997). "Identification of the naturally occurring flavin of nitroalkane oxidase from fusarium oxysporum as a 5-nitrobutyl-FAD and conversion of the enzyme to the active FAD-containing form." J Biol Chem 272(9);5563-70. PMID: 9038163
Gadda98: Gadda G, Fitzpatrick PF (1998). "Biochemical and physical characterization of the active FAD-containing form of nitroalkane oxidase from Fusarium oxysporum." Biochemistry 37(17);6154-64. PMID: 9558355
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