Heme oxygenase

Encyclopedia : H : HE : HEM : Heme oxygenase

Heme oxygenase (HO) is an enzyme that catalyzes the degradation of heme. This results in the degradation of heme and the production of iron, carbon monoxide and biliverdin. Heme oxygenase cleaves the heme ring at the alpha methene bridge to form biliverdin. Biliverdin is subsequently converted to bilirubin by biliverdin reductase.

It catalyzes the following chemical reaction:

Heme + 3 AH₂ + 3 O₂ = biliverdin + Fe²⁺ + CO + 3 A + 3 H₂O

This reaction can occur in virtually every cell, and the classical example is the formation of bruise and the changing colours which develop during its sequential disappearance (red heme to green biliverdin to yellow bilirubin). Under normal physiological conditions, the activity of heme oxygenase is highest in the spleen, where old erythrocytes are sequestrated and destroyed.

Heme oxygenase

See also