Enzymes (HSP32, EC 18.104.22.168), of which various isoforms are known, that metabolize haem to form carbon monoxide, iron, and biliverdin. Increased haem-derived CO inhibits nitric oxide synthase and is a putative neurotransmitter. Haem oxygenase-1 (HO-1, 288 aa) is an inducible heat-shock/stress protein and regulates inflammation by attenuating adhesive interactions and cellular infiltration. HO-2 (316 aa) is constitutive and present in endothelial cells, adventitial nerves of blood vessels and neurons in autonomic ganglia. The role of HO-3 is not clearly defined.
Subjects: Chemistry — Medicine and Health.