Protoporphyrinogen oxidase, also known as PPOX,'s a human gene. PPOX (protoporphyrinogen oxidase)'s a human gene that produces an enzyme called protoporphyrinogen oxidase. This enzyme's responsible for the seventh step in heme production. Heme's the portion of hemoglobin that carries oxygen in the blood from the lungs to the rest of the body. Each of the steps in heme production's controlled by a separate gene (see below). Protoporphyrinogen oxidase removes hydrogen atoms from protoporphyrinoge… (More on Ppox)