Characteristics of Protoporphyrinogen Oxidase

Protoporphyrinogen oxidase (EC 1.3.3.4) catalyzes the oxidative O2-dependent aromatization of the colorless protoporphyrinogen IX to the highly conjugated protoporphyrin IX, the precursor of both hemes and chlorophylls (Fig. 1). It is the final enzyme in the common branch of the heme and chlorophyll biosyn-thetic pathways in plants (Fig. 2).