Xenobiotics are chemicals which are found in the body but have not been produced naturally. Our body clears these chemicals using different enzymes and pathways to prevent them from reaching toxic levels and becoming harmful.
FMO is a group of enzymes which break down a number of dietary xenobiotics. A problem in the FMO3 enzyme means our body will be unable to break down a compound called trimethylamine (TMA) which enters the body from the gut, and this leads to the condition Trimethylaminuria (TMAU).