Orosomucoid

{{Short description|Acute phase protein found in plasma}}

{{infobox protein

| Name = orosomucoid 1

| caption =

| image =

| width =

| HGNCid = 8498

| Symbol = ORM1

| AltSymbols =

| EntrezGene = 5004

| OMIM = 138600

| RefSeq = NM_000607

| UniProt = P02763

| PDB =

| ECnumber =

| Chromosome = 9

| Arm = q

| Band = 31

| LocusSupplementaryData = -qter

}}

{{infobox protein

| Name = orosomucoid 2

| caption =

| image =

| width =

| HGNCid = 8499

| Symbol = ORM2

| AltSymbols =

| EntrezGene = 5005

| OMIM = 138610

| RefSeq = NM_000608

| UniProt = P19652

| PDB =

| ECnumber =

| Chromosome = 9

| Arm = q

| Band = 31

| LocusSupplementaryData = -qter

}}

Orosomucoid (ORM) or alpha-1-acid glycoprotein (α₁AGp, AGP or AAG) is an acute phase protein found in plasma. It is an alpha-globulin glycoprotein and is modulated by two polymorphic genes. It is synthesized primarily in hepatocytes and has a normal plasma concentration between 0.6–1.2 mg/mL (1–3% plasma protein).{{cite journal | vauthors = Colombo S, Buclin T, Décosterd LA, Telenti A, Furrer H, Lee BL, Biollaz J, Eap CB | title = Orosomucoid (alpha1-acid glycoprotein) plasma concentration and genetic variants: effects on human immunodeficiency virus protease inhibitor clearance and cellular accumulation | journal = Clinical Pharmacology and Therapeutics | volume = 80 | issue = 4 | pages = 307–18 | date = October 2006 | pmid = 17015049 | doi = 10.1016/j.clpt.2006.06.006 | s2cid = 684478 }} Plasma levels are affected by pregnancy, burns, certain drugs, and certain diseases, particularly HIV.

The only established function of ORM is to act as a carrier of basic and neutrally charged lipophilic compounds. In medicine, it is known as the primary carrier of basic (positively charged) drugs (whereas albumin carries acidic (negatively charged) and neutral drugs), steroids, and protease inhibitors.{{cite journal | vauthors = Urien S, Brée F, Testa B, Tillement JP | title = pH-dependency of basic ligand binding to alpha 1-acid glycoprotein (orosomucoid) | journal = The Biochemical Journal | volume = 280 ( Pt 1) | issue = 1 | pages = 277–80 | date = November 1991 | pmid = 1741754 | pmc = 1130632 | doi = 10.1042/bj2800277}} Aging causes a small decrease in plasma albumin levels; if anything, there is a small increase in alpha-1-acid glycoprotein. The effect of these changes on drug protein binding and drug delivery, however, appear to be minimal.{{cite book | vauthors = Rooke GA | chapter = Anesthesia for the Older Patient | veditors = Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC | title = Clinical Anesthesia | publisher = Lippincott Williams & Wilkins | year = 2009 | isbn = 978-0-7817-8763-5 | page = 879 }} AGP shows a complex interaction with thyroid homeostasis: AGP in low concentrations was observed to stimulate the thyrotropin (TSH) receptor and intracellular accumulation of cyclic AMP. High AGP concentrations, however, inhibited TSH signalling.{{cite journal | vauthors = Zimmermann-Belsing T, Rasmussen AK, Feldt-Rasmussen U, Bøg-Hansen TC | title = The influence of alpha1-acid glycoprotein (orosomucoid) and its glycoforms on the function of human thyrocytes and CHO cells transfected with the human TSH receptor | journal = Molecular and Cellular Endocrinology | volume = 188 | issue = 1–2 | pages = 241–51 | date = February 2002 | pmid = 11911961 | doi = 10.1016/s0303-7207(01)00650-5 | s2cid = 22815279 }}{{cite journal | vauthors = Dietrich JW, Landgrafe G, Fotiadou EH | title = TSH and Thyrotropic Agonists: Key Actors in Thyroid Homeostasis | journal = Journal of Thyroid Research | volume = 2012 | pages = 351864 | year = 2012 | pmid = 23365787 | pmc = 3544290 | doi = 10.1155/2012/351864 | doi-access = free }}

Alpha-1-acid glycoprotein has been identified as one of four potentially useful circulating biomarkers for estimating the five-year risk of all-cause mortality (the other three are albumin, very low-density lipoprotein particle size, and citrate).{{cite journal | vauthors = Fischer K, Kettunen J, Würtz P, Haller T, Havulinna AS, Kangas AJ, Soininen P, Esko T, Tammesoo ML, Mägi R, Smit S, Palotie A, Ripatti S, Salomaa V, Ala-Korpela M, Perola M, Metspalu A | title = Biomarker profiling by nuclear magnetic resonance spectroscopy for the prediction of all-cause mortality: an observational study of 17,345 persons | journal = PLOS Medicine | volume = 11 | issue = 2 | pages = e1001606 | date = February 2014 | pmid = 24586121 | pmc = 3934819 | doi = 10.1371/journal.pmed.1001606 | doi-access = free }}

Orosomucoid increases in amount in obstructive jaundice while it diminishes in hepatocellular jaundice and in intestinal infections.{{citation needed|date=March 2024}}