Intracellular oxygen transport

Globins are heme-containing proteins that reversibly bind molecular oxygen. Humans contain at least 5 types of globins: hemoglobins, myoglobin, cytoglobin, neuroglobin, and androglobin (reviewed in Burmester et al. 2014). Myoglobin, neuroglobin, and cytoglobin are cytosolic globins with similar affinities for oxygen (reviewed in Hankeln et al. 2005). Androglobin is a more distantly related globin of uncertain function that is expressed in testes. Myoglobin is predominantly expressed in muscle tissue (reviewed in Helbo et al. 2013), neuroglobin is expressed in neurons, and cytoglobin is expressed in connective tissue fibroblasts and smooth muscle cells (reviewed in Pesce et al. 2002, Hankeln et al. 2004, Ascenzi et al. 2016). Whereas myoglobin contains pentacoordinated heme iron, neuroglobin and cytoglobin contain hexacoordinated heme iron: the iron atom is bound by 4 nitrogen atoms of heme and 2 histidine residues of the globin. Binding by one of the histidines is reversible, which allows the iron atom to bind various ligands such as molecular oxygen, carbon monoxide, and nitric oxide (reviewed in Kakar et al. 2010). Neuroglobin may function in oxygen homeostasis, however the importance of its oxygen-binding activity is unclear (reviewed in Pesce et al. 2002, Hankeln et al. 2005). Cytoglobin may function in nitric oxide metabolism. Globins can also regulate oxygen homeostasis via reactions with nitric oxide (NO), a vasodilator. Oxygenated globins scavenge NO by oxidation while deoxygenated globins can act as a nitrite reductase to produce NO (reviewed in Hendgen-Cotta et al. 2014, Tejero and Gladwin 2014).

Summary from Reactome (R-HSA-8981607), read 2026-09-23.