IUBMB Enzyme Nomenclature


Accepted name: carnitine monooxygenase

Reaction: L-carnitine + NAD(P)H + H+ + O2 = (3R)-3-hydroxy-4-oxobutanoate + trimethylamine + NAD(P)+ + H2O

Glossary: (3R)-3-hydroxy-4-oxobutanoate = L-malic semialdehyde

Other name(s): cntAB (gene names); yeaWX (gene names)

Systematic name: L-carnitine,NAD(P)H:oxygen oxidoreductase (trimethylamine-forming)

Comments: The bacterial enzyme is a complex consisting of a reductase and an oxygenase components. The reductase subunit contains a flavin and a plant-type ferredoxin [2Fe-2S] cluster, while the oxygenase subunit is a Rieske-type protein in which a [2Fe-2S] cluster is coordinated by two histidine and two cysteine residues.

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


1. Ditullio, D., Anderson, D., Chen, C.S. and Sih, C.J. L-Carnitine via enzyme-catalyzed oxidative kinetic resolution. Bioorg. Med. Chem. 2 (1994) 415-420. [PMID: 8000862]

2. Zhu, Y., Jameson, E., Crosatti, M., Schafer, H., Rajakumar, K., Bugg, T.D. and Chen, Y. Carnitine metabolism to trimethylamine by an unusual Rieske-type oxygenase from human microbiota. Proc. Natl Acad. Sci. USA 111 (2014) 4268-4273. [PMID: 24591617]

3. Koeth, R.A., Levison, B.S., Culley, M.K., Buffa, J.A., Wang, Z., Gregory, J.C., Org, E., Wu, Y., Li, L., Smith, J.D., Tang, W.H., DiDonato, J.A., Lusis, A.J. and Hazen, S.L. γ-Butyrobetaine is a proatherogenic intermediate in gut microbial metabolism of L-carnitine to TMAO. Cell Metab 20 (2014) 799-812. [PMID: 25440057]

[EC created 2017]

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