Heme oxygenase-2 (HO-2) is a constitutively active heme oxygenase encoded by the HMOX2 gene. It is a membrane-bound enzyme that catalyzes the cleavage of heme to give carbon monoxide (CO), ferrous ions (Fe2+), and biliverdin, with biliverdin being further processed into bilirubin. HO-2 is found in neurons, testes, and endothelial and smooth muscle cells from cerebral vessels. HO-2 protects against apoptotic neuronal cell death in models of ischemic injury and oxidative stress. It also acts as an oxygen sensor to inhibit systemic vascular reactivity and reduce cell death in response to hypoxia.
