Carboxyhemoglobin

Not to be confused with carbaminohemoglobin, the compound formed when CO
2 binds with hemoglobin.
Carboxyhemoglobin
A heme unit of human carboxyhaemoglobin, showing the carbonyl ligand at the apical position, trans to the histidine residue.[1]
A heme unit of human carboxyhaemoglobin, showing the carbonyl ligand at the apical position, trans to the histidine residue.[1]
Names
Preferred IUPAC name
Carbonylhemoglobin
Other names
Carboxyhemoglobin
Carboxyhaemoglobin
Kohlenoxyhaemoglobin
Kohlenoxyhämoglobin
Kohlenoxydhämoglobin
Kohlenmonoxyhämoglobin
Carbonmonoxyhemoglobin
Carbon-monoxide-hemoglobin
Carbon-monoxide-Methemoglobin
Carbonic oxide hæmoglobin
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Carboxyhemoglobin (carboxyhaemoglobin BrE) (symbol COHb or HbCO) is a stable complex of carbon monoxide and hemoglobin (Hb) that forms in red blood cells upon contact with carbon monoxide. Carboxyhemoglobin is often mistaken for the compound formed by the combination of carbon dioxide (carboxyl) and hemoglobin, which is actually carbaminohemoglobin. Carboxyhemoglobin terminology emerged when carbon monoxide was known by its historic name, "carbonic oxide", and evolved through Germanic and British English etymological influences; the preferred IUPAC nomenclature is carbonylhemoglobin.[2][3][4]

The average non-smoker maintains a systemic carboxyhemoglobin level under 3% COHb whereas smokers approach 10% COHb.[4] The biological threshold for carboxyhemoglobin tolerance is 15% COHb, meaning toxicity is consistently observed at levels in excess of this concentration.[5] The FDA has previously set a threshold of 14% COHb in certain clinical trials evaluating the therapeutic potential of carbon monoxide.[6]

  1. ^ Vásquez GB, Ji X, Fronticelli C, Gilliland GL (May 1998). "Human carboxyhemoglobin at 2.2 A resolution: structure and solvent comparisons of R-state, R2-state and T-state hemoglobins". Acta Crystallographica. Section D, Biological Crystallography. 54 (Pt 3): 355–366. doi:10.1107/S0907444997012250. PMID 9761903.
  2. ^ "IUPAC Glossary of Terms Used in Toxicology - Terms Starting with C". www.nlm.nih.gov. Retrieved 2021-05-09.
  3. ^ PubChem. "Carbon monoxide". pubchem.ncbi.nlm.nih.gov. Retrieved 2021-05-09.
  4. ^ a b Hopper CP, Zambrana PN, Goebel U, Wollborn J (June 2021). "A brief history of carbon monoxide and its therapeutic origins". Nitric Oxide. 111: 45–63. doi:10.1016/j.niox.2021.04.001. PMID 33838343. S2CID 233205099.
  5. ^ Motterlini R, Foresti R (March 2017). "Biological signaling by carbon monoxide and carbon monoxide-releasing molecules". American Journal of Physiology. Cell Physiology. 312 (3): C302–C313. doi:10.1152/ajpcell.00360.2016. PMID 28077358.
  6. ^ Yang X, de Caestecker M, Otterbein LE, Wang B (July 2020). "Carbon monoxide: An emerging therapy for acute kidney injury". Medicinal Research Reviews. 40 (4): 1147–1177. doi:10.1002/med.21650. PMC 7280078. PMID 31820474.