In enzymology, a (S)-canadine synthase (EC 1.14.21.5) is an enzyme that catalyzes the chemical reaction

(S)-tetrahydrocolumbamine + NADPH + H⁺ + O₂ ${\displaystyle \rightleftharpoons }$ (S)-canadine + NADP⁺ + 2 H₂O

The 4 substrates of this enzyme are (S)-tetrahydrocolumbamine, NADPH, H⁺, and O₂, whereas its 3 products are Canadine, 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)-tetrahydrocolumbamine,NADPH:oxygen oxidoreductase (methylenedioxy-bridge-forming). Other names in common use include (S)-tetrahydroberberine synthase, and (S)-tetrahydrocolumbamine oxidase (methylenedioxy-bridge-forming). This enzyme participates in alkaloid biosynthesis i. It employs one cofactor, heme-thiolate(P-450).

• Rueffer M, Zenk MH (1994). "Canadine synthase from Thalictrum tuberosum cell cultures catalyses the formation of the methylenedioxy bridge in berberine synthesis". Phytochemistry. 36 (5): 1219–1223. doi:10.1016/S0031-9422(00)89640-5.