Involved in the degradation of the pyridine ring of trigonelline (TG; N-methylnicotinate) into succinate and methylamine as carbon and nitrogen sources, respectively. Catalyzes the insertion of two oxygens, followed by a ring cleavage of trigonelline to yield (Z)-2-((N-methylformamido)methylene)-5-hydroxybutyrolactone (MFMB). It is able to use reduced FMN or FAD. FMNH2 + N-methylnicotinate + O2 = (Z)-2-((N-methylformamido)methylene)-5-hydroxybutanolactone + FMN + H(+) FADH2 + N-methylnicotinate + O2 = (Z)-2-((N-methylformamido)methylene)-5-hydroxybutanolactone + FAD + H(+) Homodimer. The trigonelline monooxygenase is composed of a reductase component TgnA and an oxygenase component TgnB. Belongs to the bacterial luciferase oxidoreductase family.