Hemopexin

Hemopexin
Identifiers
Symbols	HPX ; HX
External IDs	OMIM: 142290 MGI: 105112 HomoloGene: 511 GeneCards: HPX Gene
EC number	3.2.1.35
Gene ontology Molecular function • protein binding • heme transporter activity • metal ion binding Cellular component • extracellular region • extracellular space • extracellular exosome • endocytic vesicle lumen • blood microparticle Biological process • positive regulation of immunoglobulin production • positive regulation of humoral immune response mediated by circulating immunoglobulin • cellular iron ion homeostasis • receptor-mediated endocytosis • heme transport • viral process • hemoglobin metabolic process • heme metabolic process • positive regulation of tyrosine phosphorylation of Stat1 protein • positive regulation of interferon-gamma-mediated signaling pathway Sources: Amigo / QuickGO
RNA expression pattern
More reference expression data
Orthologs
Species	Human	Mouse
Entrez	3263	15458
Ensembl	ENSG00000110169	ENSMUSG00000030895
UniProt	P02790	Q91X72
RefSeq (mRNA)	NM_000613	NM_017371
RefSeq (protein)	NP_000604	NP_059067
Location (UCSC)	Chr 11: 6.43 – 6.44 Mb	Chr 7: 105.59 – 105.6 Mb
PubMed search

Hemopexin (or haemopexin; HPX), also known as beta-1B-glycoprotein is a protein that in humans is encoded by the HPX gene^[1][2][3] and belongs to hemopexin family of proteins.^[4]

Function

Hemopexin binds heme with the highest affinity of any known protein. Its function is scavenging the heme released or lost by the turnover of heme proteins such as hemoglobin and thus protects the body from the oxidative damage that free heme can cause. In addition, hemopexin releases its bound ligand for internalisation upon interacting with a specific receptor situated on the surface of liver cells. This function of hemopexin is to preserve the body's iron.^[5]

Clinical significance

Its levels in serum reflect how much heme is present in the blood. Therefore, low hemopexin levels indicates that there has been significant degradation of heme containing compounds and hemopexin is made to scavenge any heme it can. Low hemopexin levels are one of the diagnostic features of an intravascular hemolytic anemia.^[6]

References

1. "Entrez Gene: HPX hemopexin".
2. Altruda F, Poli V, Restagno G, Silengo L (1988). "Structure of the human hemopexin gene and evidence for intron-mediated evolution". J. Mol. Evol. 27 (2): 102–8. doi:10.1007/BF02138368. PMID 2842511.
3. Altruda F, Poli V, Restagno G, Argos P, Cortese R, Silengo L (June 1985). "The primary structure of human hemopexin deduced from cDNA sequence: evidence for internal, repeating homology". Nucleic Acids Res. 13 (11): 3841–59. doi:10.1093/nar/13.11.3841. PMC 341281. PMID 2989777.
4. Bode W (June 1995). "A helping hand for collagenases: the haemopexin-like domain". Structure 3 (6): 527–30. doi:10.1016/s0969-2126(01)00185-x. PMID 8590012.
5. Tolosano E, Altruda F (April 2002). "Hemopexin: structure, function, and regulation". DNA Cell Biol. 21 (4): 297–306. doi:10.1089/104454902753759717. PMID 12042069.
6. Hoffbrand, A.V.; Moss, P.A.H.; Pettit, J.E. (2006). Essential Haematology (5th ed.). Oxford: Blackwell Publishing. p. 60. ISBN 978-1-4051-3649-5.

Further reading

• Piccard H, Van den Steen PE, Opdenakker G (2007). "Hemopexin domains as multifunctional liganding modules in matrix metalloproteinases and other proteins.". J. Leukoc. Biol. 81 (4): 870–92. doi:10.1189/jlb.1006629. PMID 17185359.
• Morgan WT, Muller-Eberhard U, Lamola AA (1978). "Interaction of rabbit hemopexin with bilirubin.". Biochim. Biophys. Acta 532 (1): 57–64. doi:10.1016/0005-2795(78)90447-6. PMID 620056.
• Liu HM, Atack JR, Rapoport SI (1989). "Immunohistochemical localization of intracellular plasma proteins in the human central nervous system.". Acta Neuropathol. 78 (1): 16–21. doi:10.1007/BF00687397. PMID 2735186.
• Smith A, Tatum FM, Muster P, et al. (1988). "Importance of ligand-induced conformational changes in hemopexin for receptor-mediated heme transport.". J. Biol. Chem. 263 (11): 5224–9. PMID 2833500.
• Altruda F, Poli V, Restagno G, Silengo L (1988). "Structure of the human hemopexin gene and evidence for intron-mediated evolution.". J. Mol. Evol. 27 (2): 102–8. doi:10.1007/BF02138368. PMID 2842511.
• Altruda F, Poli V, Restagno G, et al. (1985). "The primary structure of human hemopexin deduced from cDNA sequence: evidence for internal, repeating homology.". Nucleic Acids Res. 13 (11): 3841–59. doi:10.1093/nar/13.11.3841. PMC 341281. PMID 2989777.
• Taketani S, Kohno H, Naitoh Y, Tokunaga R (1987). "Isolation of the hemopexin receptor from human placenta.". J. Biol. Chem. 262 (18): 8668–71. PMID 3036819.
• Law ML, Cai GY, Hartz JA, et al. (1989). "The hemopexin gene maps to the same location as the beta-globin gene cluster on human chromosome 11.". Genomics 3 (1): 48–52. doi:10.1016/0888-7543(88)90158-9. PMID 3220477.
• Morgan WT, Alam J, Deaciuc V, et al. (1988). "Interaction of hemopexin with Sn-protoporphyrin IX, an inhibitor of heme oxygenase. Role for hemopexin in hepatic uptake of Sn-protoporphyrin IX and induction of mRNA for heme oxygenase.". J. Biol. Chem. 263 (17): 8226–31. PMID 3372522.
• Takahashi N, Takahashi Y, Putnam FW (1985). "Complete amino acid sequence of human hemopexin, the heme-binding protein of serum.". Proc. Natl. Acad. Sci. U.S.A. 82 (1): 73–7. doi:10.1073/pnas.82.1.73. PMC 396973. PMID 3855550.
• Takahashi N, Takahashi Y, Putnam FW (1984). "Structure of human hemopexin: O-glycosyl and N-glycosyl sites and unusual clustering of tryptophan residues.". Proc. Natl. Acad. Sci. U.S.A. 81 (7): 2021–5. doi:10.1073/pnas.81.7.2021. PMC 345428. PMID 6371807.
• Frantíková V, Borvák J, Kluh I, Morávek L (1985). "Amino acid sequence of the N-terminal region of human hemopexin.". FEBS Lett. 178 (2): 213–6. doi:10.1016/0014-5793(84)80603-1. PMID 6510521.
• Smith A, Alam J, Escriba PV, Morgan WT (1993). "Regulation of heme oxygenase and metallothionein gene expression by the heme analogs, cobalt-, and tin-protoporphyrin.". J. Biol. Chem. 268 (10): 7365–71. PMID 8463269.
• Morris CM, Candy JM, Edwardson JA, et al. (1993). "Evidence for the localization of haemopexin immunoreactivity in neurones in the human brain.". Neurosci. Lett. 149 (2): 141–4. doi:10.1016/0304-3940(93)90756-B. PMID 8474687.
• Hrkal Z, Kuzelová K, Muller-Eberhard U, Stern R (1996). "Hyaluronan-binding properties of human serum hemopexin.". FEBS Lett. 383 (1-2): 72–4. doi:10.1016/0014-5793(96)00225-6. PMID 8612795.
• Hunt RC, Hunt DM, Gaur N, Smith A (1996). "Hemopexin in the human retina: protection of the retina against heme-mediated toxicity.". J. Cell. Physiol. 168 (1): 71–80. doi:10.1002/(SICI)1097-4652(199607)168:1<71::AID-JCP9>3.0.CO;2-5. PMID 8647924.
• Miller YI, Smith A, Morgan WT, Shaklai N (1996). "Role of hemopexin in protection of low-density lipoprotein against hemoglobin-induced oxidation.". Biochemistry 35 (40): 13112–7. doi:10.1021/bi960737u. PMID 8855948.
• Grinberg LN, O'Brien PJ, Hrkal Z (1999). "The effects of heme-binding proteins on the peroxidative and catalatic activities of hemin.". Free Radic. Biol. Med. 27 (1-2): 214–9. doi:10.1016/S0891-5849(99)00082-9. PMID 10443938.
• Nakajima S, Moriyama T, Hayashi H, et al. (2000). "Hemopexin as a carrier protein of tumor-localizing Ga-metalloporphyrin-ATN-2.". Cancer Lett. 149 (1-2): 221–6. doi:10.1016/S0304-3835(99)00367-5. PMID 10737728.
• Shipulina N, Smith A, Morgan WT (2001). "Heme binding by hemopexin: evidence for multiple modes of binding and functional implications.". J. Protein Chem. 19 (3): 239–48. doi:10.1023/A:1007016105813. PMID 10981817.

External links

• Hemopexin at the US National Library of Medicine Medical Subject Headings (MeSH)

See also

• Haptoglobin
• Hemoglobin
• Heme