Methylamine dehydrogenase (amicyanin)

Methylamine dehydrogenase catalyzes the reduction of copper-dependent electron-carrier amicyanin via oxidation of methylamine to formaldehyde.
This reaction requires the post-translational formation of a tryptophan tryptophylquinone cofactor. MADH forms a tetramer of two light-chain and two heavy-chain protomers. The TTQ cofactor is located in the light-chain and is formed from oxidative coupling between Trp57 and Trp108 catalyzed by the diheme enzyme MauG.
In P. denitrificans, methylamine dehydrogenase 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.