In enzymology, a trimethylamine-N-oxide reductase is an enzyme that catalyzes the chemical reaction trimethylamine + 2 -subunit + H2O ⇌ {\displaystyle \rightleftharpoons } trimethylamine N-oxide + 2 -subunit + 2 H+The 3 substrates of this enzyme are trimethylamine, -subunit, and H2O, whereas its 3 products are trimethylamine N-oxide, -subunit, and H+.