heme catabolic process

Definition

Target type: biologicalprocess

The chemical reactions and pathways resulting in the breakdown of heme, any compound of iron complexed in a porphyrin (tetrapyrrole) ring. [GOC:jl]

Heme catabolism is a crucial biological process responsible for the breakdown of heme, a porphyrin ring complex containing iron, found in hemoglobin, myoglobin, and other heme proteins. It is a tightly regulated process involving a series of enzymatic reactions that occur primarily in the spleen, liver, and bone marrow.

The process begins with the removal of heme from its protein carrier, often hemoglobin, through the action of heme oxygenase (HO). HO catalyzes the oxidative cleavage of the porphyrin ring, using molecular oxygen and NADPH as cofactors. This reaction generates biliverdin, a green pigment, ferrous iron (Fe2+), and carbon monoxide (CO).

Biliverdin is then reduced to bilirubin, a yellow pigment, by biliverdin reductase. Bilirubin is transported in the blood bound to albumin to the liver. In the liver, bilirubin undergoes conjugation with glucuronic acid, forming bilirubin diglucuronide, a water-soluble compound that can be excreted in the bile.

The iron released from heme is recycled and incorporated into new heme molecules or stored in the liver as ferritin. Carbon monoxide, while considered a toxic gas, has also been shown to have physiological roles in signaling and regulation.

The heme catabolic process is essential for maintaining iron homeostasis, removing potentially toxic heme, and generating pigments for bile production. Defects in this pathway can lead to various diseases, including jaundice, porphyria, and iron overload disorders.'
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Proteins (14)

Compounds (876)