Greater celandine, similarly as other plants of the family Papaveraceae, produces benzylisoquinoline alkaloids, primarily benzophenanthridines. Polyphenoloxidase (PPO) is most probably involved in the formation of dopamine, which is one of the precursors of norcoclaurine, the first intermediate with the benzylisoquinoline structure. This study has revealed that PPO present in the latex of greater celandine is localized in the organelles, which serve to store alkaloids (the so-called 1000 g organelles). The enzyme was purified by means of affinity chromatography into electrophoretic homogeneity. It possesses a relative molecular mass of approximately 65 kDa and exerts two activities, the monophenolase and diphenolase ones. With the use of a polymerase chain reaction, it was possible to amplify a part of the PPO gene from the region of the active site.