Wiktionary
n. (context enzyme English) An enzyme responsible for the seventh step in heme production, removing hydrogen atoms from protoporphyrinogen IX to form protoporphyrin IX.
Wikipedia
Protoporphyrinogen oxidase is an enzyme that in humans is encoded by the PPOX gene.
Protoporphyrinogen oxidase is responsible for the seventh step in biosynthesis of protoporphyrin IX. This porphyrin is the precursor to hemoglobin, the oxygen carrier in animals, and chlorophyll, the dye in plants. The enzyme catalyzes the dehydrogenation (removal of hydrogen atoms) of protoporphyrinogen IX (the product of the sixth step in the production of heme) to form protoporphyrin IX. One additional enzyme must modify protoporphyrin IX before it becomes heme. Inhibition of this enzyme is a strategy used in certain herbicides.