(S)-tetrahydroprotoberberine N-methyltransferase activity
(s)-tetrahydroprotoberberine n-methyltransferase activity
Catalysis of the reaction: an (S)-7,8,13,14-tetrahydroprotoberberine + S-adenosyl-L-methionine = an (S)-cis-N-methyl-7,8,13,14-tetrahydroprotoberberine + S-adenosyl-L-homocysteine.