N-methyltransferase with a broad substrate range, accepting protoberberine alkaloids (R,S)-stylopine and (R,S)-tetrahydropalmatine, and to a lesser extent (R,S)-canadine and (S)-scoulerine. (S)-canadine + S-adenosyl-L-methionine = (S)-N-methylcanadine + S-adenosyl-L-homocysteine Homodimer. Up-regulated 2 hours after elicitor treatment. Belongs to the CFA/CMAS family.