IUBMB Enzyme Nomenclature


Accepted name: toluene methyl-monooxygenase

Reaction: (1) toluene + O2 + 2 reduced ferredoxin [iron-sulfur] cluster + 2 H+ = benzyl alcohol + 2 oxidized ferredoxin [iron-sulfur] cluster + H2O
(2) p-xylene + O2 + 2 reduced ferredoxin [iron-sulfur] cluster + 2 H+ = 4-methylbenzyl alcohol + 2 oxidized ferredoxin [iron-sulfur] cluster + H2O
(3) m-xylene + O2 + 2 reduced ferredoxin [iron-sulfur] cluster + 2 H+ = 3-methylbenzyl alcohol + 2 oxidized ferredoxin [iron-sulfur] cluster + H2O

Glossary: toluene = methylbenzene
p-xylene = 1,4-dimethylbenzene
m-xylene = 1,3-dimethylbenzene

Other name(s): xylM (gene names); ntnM (gene names)

Systematic name: methylbenzene,ferredoxin:oxygen oxidoreductase (methyl-hydroxylating)

Comments: The enzyme, characterized from several Pseudomonas strains, catalyses the first step in the degradation of toluenes and xylenes. It has a broad substrate specificity and is also active with substituted compounds, such as chlorotoluenes. The electrons are provided by a reductase (EC, ferredoxin—NAD+ reductase) that transfers electrons from NADH via FAD and an [2Fe-2S] cluster. The enzyme can also act on its products, producing gem-diols that spontaneously dehydrate to form aldehydes.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:


1. Suzuki, M., Hayakawa, T., Shaw, J.P., Rekik, M. and Harayama, S. Primary structure of xylene monooxygenase: similarities to and differences from the alkane hydroxylation system. J. Bacteriol. 173 (1991) 1690-1695. [PMID: 1999388]

2. Shaw, J.P. and Harayama, S. Purification and characterisation of the NADH:acceptor reductase component of xylene monooxygenase encoded by the TOL plasmid pWW0 of Pseudomonas putida mt-2. Eur. J. Biochem. 209 (1992) 51-61. [PMID: 1327782]

3. Brinkmann, U. and Reineke, W. Degradation of chlorotoluenes by in vivo constructed hybrid strains: problems of enzyme specificity, induction and prevention of meta-pathway. FEMS Microbiol. Lett. 75 (1992) 81-87. [PMID: 1526468]

4. James, K.D. and Williams, P.A. ntn genes determining the early steps in the divergent catabolism of 4-nitrotoluene and toluene in Pseudomonas sp. strain TW3. J. Bacteriol. 180 (1998) 2043-2049. [PMID: 9555884]

[EC created 2018]

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