Protoporphyrinogen oxidase

An enzyme involved in heme biosynthesis

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Protoporphyrinogen oxidase

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Overview of heme synthesis, showing the role of protoporphyrinogen oxidase.

Protoporphyrinogen oxidase (PPOX) is an enzyme that plays a crucial role in the biosynthesis of heme, an essential component of hemoglobin, myoglobin, and various cytochromes. This enzyme catalyzes the oxidation of protoporphyrinogen IX to protoporphyrin IX, a key step in the heme synthesis pathway.

Function

Protoporphyrinogen oxidase is located in the mitochondrial membrane and is responsible for the seventh step in the heme biosynthetic pathway. The enzyme facilitates the conversion of protoporphyrinogen IX, a colorless compound, into protoporphyrin IX, a colored compound, by removing six hydrogen atoms. This reaction is crucial for the subsequent incorporation of iron to form heme.

Structure

PPOX is a flavoprotein, meaning it contains a flavin adenine dinucleotide (FAD) cofactor that is essential for its enzymatic activity. The enzyme is encoded by the PPOX gene, which is located on chromosome 1 in humans. Mutations in this gene can lead to disorders such as variegate porphyria.

Clinical significance

Deficiencies or malfunctions in protoporphyrinogen oxidase can result in a group of disorders known as porphyrias. These are metabolic disorders characterized by an accumulation of porphyrins or porphyrin precursors, leading to a variety of symptoms including skin photosensitivity, abdominal pain, and neurological complications.

Related pages

• Heme
• Porphyria
• Cytochrome
• Hemoglobin
• Myoglobin