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 → Aromatic Compounds Degradation → Toluenes Degradation|
Expected Taxonomic Range: Proteobacteria
Several microorganisms have been isolated which are capable of degrading toluene via various mechanisms.
Pseudomonas mendocina KR1 is capable of using toluene as a sole carbon and energy source, converting it to substrates of the tricarboxylic acid cycle. Unlike the other pathways of microbial toluene degradation, which involves meta cleavage of the aromatic ring, the enzymes in this degradation pathway use ortho ring cleavage [Whited91].
The initial step in this pathway involves the hydroxylation of toluene by EC 1.14.13.M1, toluene-4-monooxygenase, to form 4-methylphenol (p-cresol) [Yen91]. p-Cresol is subsequently converted to 4-hydroxybenzaldehyde by a flavocytochrome, EC 184.108.40.206, 4-methylphenol dehydrogenase (hydroxylating) [McIntire86]. 4-Hydroxybenzaldehyde is then oxidized by an NAD+- or NADP+-dependent dehydrogenase to form 4-hydroxybenzoate [Bossert89], which is hydroxylated to form protocatechuate. The latter is completely dissimilated by an ortho cleavage pathway [Whited91].
Superpathways: superpathway of aerobic toluene degradation
Variants: 2,4-xylenol degradation to protocatechuate, toluene degradation I (aerobic) (via o-cresol), toluene degradation II (aerobic) (via 4-methylcatechol), toluene degradation IV (aerobic) (via catechol), toluene degradation to 2-oxopent-4-enoate (via 4-methylcatechol), toluene degradation to 2-oxopent-4-enoate (via toluene-cis-diol), toluene degradation to 2-oxopent-4-enoate I (via o-cresol), toluene degradation to benzoate, toluene degradation to benzoyl-CoA (anaerobic), toluene degradation V (aerobic) (via toluene-cis-diol), toluene degradation VI (anaerobic)
Bossert89: Bossert ID, Whited G, Gibson DT, Young LY (1989). "Anaerobic oxidation of p-cresol mediated by a partially purified methylhydroxylase from a denitrifying bacterium." J Bacteriol 1989;171(6);2956-62. PMID: 2722739
Johnson06: Johnson DR, Park J, Kukor JJ, Abriola LM (2006). "Effect of carbon starvation on toluene degradation activity by toluene monooxygenase-expressing bacteria." Biodegradation NIL;1-9. PMID: 16477358
McIntire86: McIntire W, Singer TP, Smith AJ, Mathews FS (1986). "Amino acid and sequence analysis of the cytochrome and flavoprotein subunits of p-cresol methylhydroxylase." Biochemistry 1986;25(20);5975-81. PMID: 3790500
Whited91: Whited GM, Gibson DT (1991). "Separation and partial characterization of the enzymes of the toluene-4-monooxygenase catabolic pathway in Pseudomonas mendocina KR1." J Bacteriol 173(9);3017-20. PMID: 2019564
Yen91: Yen KM, Karl MR, Blatt LM, Simon MJ, Winter RB, Fausset PR, Lu HS, Harcourt AA, Chen KK (1991). "Cloning and characterization of a Pseudomonas mendocina KR1 gene cluster encoding toluene-4-monooxygenase." J Bacteriol 1991;173(17);5315-27. PMID: 1885512
Bull81: Bull C, Ballou DP (1981). "Purification and properties of protocatechuate 3,4-dioxygenase from Pseudomonas putida. A new iron to subunit stoichiometry." J Biol Chem 256(24);12673-80. PMID: 6273403
Canovas67: Canovas JL, Ornston LN, Stanier RY (1967). "Evolutionary significance of metabolic control systems. The beta-ketoadipate pathway provides a case history in bacteria." Science 156(783);1695-9. PMID: 5611030
Cerini04: Cerini C, Dou L, Anfosso F, Sabatier F, Moal V, Glorieux G, De Smet R, Vanholder R, Dignat-George F, Sampol J, Berland Y, Brunet P (2004). "P-cresol, a uremic retention solute, alters the endothelial barrier function in vitro." Thromb Haemost 92(1);140-50. PMID: 15213855
Chen14: Chen YF, Chao H, Zhou NY (2014). "The catabolism of 2,4-xylenol and p-cresol share the enzymes for the oxidation of para-methyl group in Pseudomonas putida NCIMB 9866." Appl Microbiol Biotechnol 98(3);1349-56. PMID: 23736872
Cronin99a: Cronin CN, Kim J, Fuller JH, Zhang X, McIntire WS (1999). "Organization and sequences of p-hydroxybenzaldehyde dehydrogenase and other plasmid-encoded genes for early enzymes of the p-cresol degradative pathway in Pseudomonas putida NCIMB 9866 and 9869." DNA Seq 10(1);7-17. PMID: 10565539
Dean89: Dean HF, Cheevadhanarak S, Skurray RA, Bayly RC (1989). "Characterisation of a degradative plasmid in Pseudomonas putida that controls the expression of 2,4-xylenol degradative genes." FEMS Microbiology Letters 61(1-2);153-158.
Efimov04: Efimov I, McIntire WS (2004). "A study of the spectral and redox properties and covalent flavinylation of the flavoprotein component of p-cresol methylhydroxylase reconstituted with FAD analogues." Biochemistry 43(32);10532-46. PMID: 15301551
Ferrandez98: Ferrandez A, Minambres B, Garcia B, Olivera ER, Luengo JM, Garcia JL, Diaz E (1998). "Catabolism of phenylacetic acid in Escherichia coli. Characterization of a new aerobic hybrid pathway." J Biol Chem 1998;273(40);25974-86. PMID: 9748275
Frazee93: Frazee RW, Livingston DM, LaPorte DC, Lipscomb JD (1993). "Cloning, sequencing, and expression of the Pseudomonas putida protocatechuate 3,4-dioxygenase genes." J Bacteriol 175(19);6194-202. PMID: 8407791
Gunsalus53: Gunsalus CF, Stanier RY, Gunsalus IC (1953). "The enzymatic conversion of mandelic acid to benzoic acid. III. Fractionation and properties of the soluble enzymes." J Bacteriol 66(5);548-53. PMID: 13108854
Halak06: Halak S, Basta T, Burger S, Contzen M, Stolz A (2006). "Characterization of the genes encoding the 3-carboxy-cis,cis-muconate-lactonizing enzymes from the 4-sulfocatechol degradative pathways of Hydrogenophaga intermedia S1 and Agrobacterium radiobacter S2." Microbiology 152(Pt 11);3207-16. PMID: 17074892
Hammer96: Hammer A, Stolz A, Knackmuss H (1996). "Purification and characterization of a novel type of protocatechuate 3,4-dioxygenase with the ability to oxidize 4-sulfocatechol." Arch Microbiol 166(2);92-100. PMID: 8772173
Harwood94: Harwood CS, Nichols NN, Kim MK, Ditty JL, Parales RE (1994). "Identification of the pcaRKF gene cluster from Pseudomonas putida: involvement in chemotaxis, biodegradation, and transport of 4-hydroxybenzoate." J Bacteriol 176(21);6479-88. PMID: 7961399
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