Oxidoreductase involved in the biosynthesis of cannabinoids-related terpenophenolic natural products, which have pharmacological activity (PubMed:17544411, PubMed:8663284). Catalyzes the stereoselective oxidative cyclization of the monoterpene moiety in cannabigerolic acid (CBGA), producing cannabidiolate (CBDA), the major cannabioid in fiber-type Cannabis plants (PubMed:17544411, PubMed:8663284). Can also use cannabinerolic acid as substrate, but not cannabigerol or cannabinerol (PubMed:17544411, PubMed:8663284). cannabigerolate + O2 = cannabidiolate + H2O2 Binds 1 FAD per subunit in a bicovalent manner. Inhibited by Hg(2+). Optimum pH is 5.0. Secondary metabolite biosynthesis; terpenoid biosynthesis. Monomer. Probably sorted from the secretory cells into the storage cavity of glandular trichomes. Expressed in young leaves. Glycosylated. The FAD cofactor is bound via a bicovalent 6-S-cysteinyl, 8alpha-N1-histidyl FAD linkage. CBDA synthase might contribute to the self-defense of Cannabis plants by producing both CBDA and hydrogen peroxide, but since these reaction products are toxic to the plant itself, CBDA synthase is probably secreted from secretory cells into the storage cavity to avoid cellular damage. Belongs to the oxygen-dependent FAD-linked oxidoreductase family.