title: The heme oxygenase system: a regulator of second messenger gases.
abstract: The heme oxygenase (HO) system consists of two forms identified to date: the oxidative stress-inducible protein HO-1 (HSP32) and the constitutive isozyme HO-2. These proteins, which are different gene products, have little in common in primary structure, regulation, or tissue distribution. Both, however, catalyze oxidation of heme to biologically active molecules: iron, a gene regulator; biliverdin, an antioxidant; and carbon monoxide, a heme ligand. Finding the impressive heme-degrading activity of brain led to the suggestion that "HO in brain has functions aside from heme degradation" and to subsequent exploration of carbon monoxide as a promising and potentially significant messenger molecule. There is much parallelism between the biological actions and functions of the CO- and NO-generating systems; and their regulation is intimately linked. This review highlights the current information on molecular and biochemical properties of HO-1 and HO-2 and addresses the possible mechanisms for mutual regulatory interactions between the CO- and NO-generating systems.
authors.affiliation: Department of Biophysics, University of Rochester School of Medicine, New York 14642, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Maines
mesh_terms: D000818:Animals; D002248:Carbon Monoxide / Q000378:metabolism; D002319:Cardiovascular System / Q000378:metabolism; D006419:Heme Oxygenase (Decyclizing) / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D051547:Heme Oxygenase-1; D006801:Humans; D008099:Liver / Q000378:metabolism; D008565:Membrane Proteins; D009420:Nervous System / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D015290:Second Messenger Systems; D014018:Tissue Distribution; D014566:Urogenital System / Q000378:metabolism
chemical_list: D008565:Membrane Proteins; D009569:Nitric Oxide; D002248:Carbon Monoxide; C496541:HMOX1 protein, human; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; C105245:heme oxygenase-2