Polyphenoloxidase-activity and -activation in embryogenic and non-embryogenic suspension cultures of Euphorbia pulcherrima.

The activity and activation potential of polyphenoloxidase (PPO, E.C. 1.10.3.1.) of tissue from shoot tips, adult leaves and embryogenic and non-embryogenic cell suspension cultures of Euphorbia pulcherrima was investigated using an oxygen probe technique. PPO derived from differentiated in vivo plant tissue (shoot tips, leaves) cannot be activated either by storage at 0-4°, freezing and thawing, incubation with CaCl2, sodium dodecyl sulfate or by incubation with trypsin. Embryogenic cells are characterized by high initial PPO activity and strong activation potential of membrane bound enzyme. Non-embryogenic material reveals low phenolase activity and low activation potential. An activation quotient (based on the ratio between "PPO-activity determined after sodium dodecyl sulfate incubation" to "PPO-activity determined after CaCl2-incubation") was calculated. This is independent of absolute enzyme activity and can be used for characterization of the embryogenic status of cells.