Trimethylamine N-oxide (
TMAO) is the
organic compound in the class of
amine oxides with the
formula (CH
3)
3NO. This colorless solid is usually encountered as the
dihydrate. It is a product of the oxidation of
trimethylamine and a common
metabolite in animals. It is an
osmolyte found in saltwater fish, sharks, rays, molluscs, and crustaceans. It is a protein stabilizer that may serve to counteract
urea, the major osmolyte of sharks, skates and rays. It is also higher in deep-sea fishes and crustaceans, where it may counteract the protein-destabilizing effects of pressure. TMAO decomposes to
trimethylamine (TMA), which is the main
odorant that is characteristic of degrading seafood.