Methyltransferase involved in the biosynthesis of the benzylisoquinoline alkaloid noscapine (By similarity). Catalyzes the conversion of (S)-scoulerine to (S)-tetrahydrocolumbamine (By similarity). The heterodimers OMT2B-SOMT3 and OMT2B-6OMT do not possess 3-O-acetyl-4'-O-demethylpapaveroxine 4'-O-methyltransferase activity (PubMed:29723437). (S)-scoulerine + S-adenosyl-L-methionine = (S)-tetrahydrocolumbamine + H(+) + S-adenosyl-L-homocysteine Alkaloid biosynthesis. A single amino acid substitution of Ser-122 in cultivar Bea's Choice (AC I3PLQ6) to Tyr-122 in cultivar Marianne (AC A0A2S1WBY6) abolishes the 3-O-acetyl-4'-O-demethylpapaveroxine 4'-O-methyltransferase activity. Belongs to the class I-like SAM-binding methyltransferase superfamily. Cation-independent O-methyltransferase family. COMT subfamily.