In enzymology, a berbamunine synthase (EC 1.14.19.66, Formerly EC 1.1.3.34 and EC 1.14.21.3) is an enzyme that catalyzes the chemical reaction

(S)-N-methylcoclaurine + (R)-N-methylcoclaurine + NADPH + H⁺ + O₂ ${\displaystyle \rightleftharpoons }$ berbamunine + NADP⁺ + 2 H₂O

The 5 substrates of this enzyme are (S)-N-methylcoclaurine, (R)-N-methylcoclaurine, NADPH, H⁺, and O₂, whereas its 3 products are berbamunine, NADP⁺, and H₂O.

This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O₂ as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O₂ with NADH or NADPH as one donor, and the other dehydrogenated. The systematic name of this enzyme class is (S)-N-methylcoclaurine,NADPH:oxygen oxidoreductase (C-O phenol-coupling). This enzyme is also called (S)-N-methylcoclaurine oxidase (C-O phenol-coupling). This enzyme participates in alkaloid biosynthesis i.

• Stadler R, Zenk MH (1993). "The purification and characterization of a unique cytochrome P-450 enzyme from Berberis stolonifera plant cell cultures". J. Biol. Chem. 268 (2): 823–31. PMID 8380416.