In vitro enzyme activity of purified recombinant proteins provided with naringenin as substrate. A, HPLC profiles of reaction products derived from various 2-ODD enzymes from different plant species, the empty vector control, and the standards. Api, Apigenin; DHK, dihydrokaempferol; Nar, Naringenin; 2-OHNar, 2-hydroxynaringenin. B, MS/MS profiles of the reactions P1 (a), P2 (c), and P3 (d), apigenin standard (b), and dihydrokaempferol standard (e).