Amine Dehydrogenase (EC 1.4.99.3), also known as methylamine dehydrogenase (MADH), is a tryptophan tryptophylquinone-dependent (TTQ-dependent) enzyme that catalyzes the oxidative deamination of a primary amine to an aldehyde and ammonia. The reaction occurs as follows:
RCH2NH2 + H2O + acceptor → RCHO + NH3 + reduced acceptor
Amine dehydrogenase possesses an α2β2 structure with each smaller β subunit possessing a TTQ protein cofactor.
Amine dehydrogenase, studied in Paracoccus denitrificans, at least transiently forms a ternary complex to catalyze methylamine-dependent cytochrome c-551i reduction. Within this complex, electrons are transferred from the TTQ cofactor of MADH to the Type 1 copper center of amicyanin, and then to the heme of the cytochrome.