Protoporphyrinogen-Oxidase

The protoporphyrinogen oxidase (PPO ) ( Gen: PPOX ) is the enzyme that catalyzes the last reaction step in the common metabolic pathway for the preparation of heme and chlorophyll. The PPO is present in almost all organisms. All eukaryotes have the enzyme in their mitochondria. In humans, PPO is produced in the heart, brain, lung, placenta, liver, skeletal muscle, kidney and pancreas. Mutations in PPOX can cause a severe metabolic disease, porphyria variegata.

In plants, in addition to mitochondrial exists also a chloroplastisches isoenzyme. A prokaryotic type of PPO, the HemG said enzyme of gram-positive bacteria that is not found in Gram-negative bacteria.

Function

PPO catalyses the six electron oxidation of protoporphyrinogen IX to protoporphyrin IX by a FAD - cofactor bound non-covalently with the involvement of molecular oxygen (O2). The substrate is planarized here and flavored by removing two hydrogen atoms on the Pyrrolstickstoffen. The product is the first of the porphyrin in Porphyrinbiosynthese and by the insertion of iron ( II) ions via ferrochelatase to Protohem IX or heme b, by the insertion of magnesium ions to Magnesioprotoporphyrin IX ( Magnesiumchelatase ), which is further processed in several steps to the chlorophyll.

Human Genome Organisation Variegate porphyria Cofactor (biochemistry)
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