Four molecules of porphobilinogen combine to form a linear tetrapyrrole, which cyclizes to uroporphyrinogen III . Oxidation and side-chain modifications lead to the synthesis of protoporphyrin IX, which acquires an iron atom to form heme.
42.
This gene encodes the penultimate enzyme of heme biosynthesis, which catalyzes the 6-electron oxidation of protoporphyrinogen IX to form protoporphyrin IX . This protein is a flavoprotein associated with the outer surface of the inner mitochondrial membrane.
43.
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.
44.
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.
45.
As a result of absorption of ultraviolet light ( that is, wavelengths less than 400 nm ) by protoporphyrin in plasma and erythrocytes when blood circulates through the dermal vessels, free radicals are formed, erythrocytes become unstable and injury to the skin is induced.
46.
To date, the U . S . Food and Drug Administration has only found a verifiable connection between ethoxyquin and buildup of protoporphyrin IX in the liver, as well as elevations in liver-related enzymes in some animals, but with no known health consequences from these effects.
47.
Saflufenacil works by inhibiting protoporphyrinogen IX oxidase ( PPO ), resulting in in planta accumulations of protoporphyrin IX ( proto ) and H2O2; inhibiting PPO formation results in prevention of chlorophyll, heme, and cytochrome synthesis; also, proto accumulation causes lipid peroxidation, resulting in rapid loss of membrane integrity and function; only slight increases of proto and H2O2 occur in corn.
