Reactome: A Curated Pathway Database

FMO3:FAD N-oxidises TMA to TMAO (R-HSA-139970) [Homo sapiens]


Trimethylamine (TMA) is present in the diet (in fish) but primarily formed in vivo from the breakdown of choline. It is N-oxidised by FMO3 in the liver, the major isoform active towards TMA, to form trimethylamine-N-oxide (TMAO). Trimethylaminuria (fish-odour syndrome) is a human genetic disorder characterised by an impaired ability to convert the malodourous TMA to the odourless N-oxide form TMAO (Higgins et al. 1972, Humbert et al. 1970, Treacy et al. 1998). L-carnitine is an abundant component of red meat and contains a trimethylamine structure similar to that of choline. Gut microbiota is able to produce TMAO from L-carnitine. If high levels of L-carnitine via high red meat intake or dietary supplements is achieved, Koeth et al. have shown the resultant TMAO produced in the gut can accelerate atherosclerosis in mice and increase the risk of cardiovascular disease (CVD) (Koeth et al. 2013).

Additional Information
Compartment endoplasmic reticulum lumen , endoplasmic reticulum membrane
Components of this entry
Input entries
Output entries
Catalyst Activity
PhysicalEntity Activity Active Units
FMO3:FAD N,N-dimethylaniline monooxygenase activity (0004499)  
Cross References
Database Identifier
Rhea 31982, 31980