albumin

Albumins in general are transport proteins that bind to various ligands and carry them around. Human types include:

• Human serum albumin is the main protein of human blood plasma. It makes up around 50% of human plasma proteins. It binds water, cations (such as Ca²⁺, Na⁺ and K⁺), fatty acids, hormones, bilirubin, thyroxine (T4) and pharmaceuticals (including barbiturates). Its main function is to regulate the oncotic pressure of blood.{{cite journal | vauthors = Farrugia A | title = Albumin usage in clinical medicine: tradition or therapeutic? | journal = Transfusion Medicine Reviews | volume = 24 | issue = 1 | pages = 53–63 | date = January 2010 | pmid = 19962575 | doi = 10.1016/j.tmrv.2009.09.005 }} The isoelectric point of albumin is 4.7.{{Cite web |date=|publisher=Sigma Aldrich |title=Product Information data sheet |url=https://www.sigmaaldrich.com/deepweb/assets/sigmaaldrich/product/documents/308/595/05420dat.pdf}}
• Alpha-fetoprotein is a fetal plasma protein that binds various cations, fatty acids and bilirubin.
• Vitamin D-binding protein binds to vitamin D and its metabolites, as well as to fatty acids.
• Not much is known about afamin. It seems to carry lipidated Wnt proteins and Vitamin E around.{{cite journal | vauthors = Mihara E, Hirai H, Yamamoto H, Tamura-Kawakami K, Matano M, Kikuchi A, Sato T, Takagi J | title = Active and water-soluble form of lipidated Wnt protein is maintained by a serum glycoprotein afamin/α-albumin | journal = eLife | volume = 5 | date = February 2016 | pmid = 26902720 | doi = 10.7554/eLife.11621 | pmc = 4775226 | doi-access = free }}
• Extracellular matrix protein 1 is a less canonical albumin. It regulates bone mineralization.

The four canonical human albumins are arranged on chromosome 4 region 4q13.3 in a tandem manner.{{cite journal | vauthors = Nishio H, Heiskanen M, Palotie A, Bélanger L, Dugaiczyk A | title = Tandem arrangement of the human serum albumin multigene family in the sub-centromeric region of 4q: evolution and chromosomal direction of transcription | journal = Journal of Molecular Biology | volume = 259 | issue = 1 | pages = 113–9 | date = May 1996 | pmid = 8648639 | doi = 10.1006/jmbi.1996.0306 }}

Albumins found in animals can be divided into six subfamilies by phylogeny. The Vitamin-D binding proteins occupy families 1–3. The other albumins are mixed among each other in families 4–6. ECM1 is in family 6.

In addition to their medical use, serum albumins are valued in biotechnology. Bovine serum albumin is usually used, although versions from humans and genetically modified rice are also used to reduce animal cruelty.

A few other proteins are also sometimes called albumins. They are not in the same family as vertebrate albumins:

• Ovalbumin is a storage protein in egg white (albumen). It is a serpin.
• Lactalbumin, or whey protein, is a protein fraction of milk. It is mainly Beta-lactoglobulin, although serum albumin also comprises a small part of it.
• Some plant seeds, including hemp, encode "2S albumins". These are named for their egg-like coagulation property.{{cite book | vauthors = Shewry PR, Pandya MJ |title=Seed Proteins |url=https://archive.org/details/seedproteins00shew |url-access=limited |publisher=Springer Netherlands |isbn=978-94-011-4431-5 |chapter=The 2S Albumin Storage Proteins |year=1999 |pages=[https://archive.org/details/seedproteins00shew/page/n577 563]–586 |doi=10.1007/978-94-011-4431-5_24}}

The 3D structure of human serum albumin has been determined by X-ray crystallography to a resolution of

{{Convert|2.5|Å|pm}}.{{cite journal | vauthors = Sugio S, Kashima A, Mochizuki S, Noda M, Kobayashi K | title = Crystal structure of human serum albumin at 2.5 A resolution | journal = Protein Engineering | volume = 12 | issue = 6 | pages = 439–46 | date = June 1999 | pmid = 10388840 | doi = 10.1093/protein/12.6.439 | doi-access = }} Albumin is a 65–70 kDa protein.

Albumin comprises three homologous domains that assemble to form a heart-shaped protein. Each domain is a product of two subdomains that possess common structural motifs. The principal regions of ligand binding to human serum albumin are located in hydrophobic cavities in subdomains IIA and IIIA, which exhibit similar chemistry. Structurally, the serum albumins are similar, each domain containing five or six internal disulfide bonds.

Worldwide, certain traditional Chinese medicines contain wild bear bile, banned under CITES legislation. Dip sticks, similar to common pregnancy tests, have been developed to detect the presence of bear albumin in traditional medicine products, indicating that bear bile had been used in their creation.{{cite journal | vauthors = Peppin L, McEwing R, Webster S, Rogers A, Nicholls D, Ogden R | title = Development of a field test for the detection of illegal bear products | journal = Endangered Species Research| date = September 2008 | volume = 9 | issue = 3 | pages = 263–70 | doi = 10.3354/esr00131 | url = https://www.int-res.com/articles/esr2009/9/n009p263.pdf | doi-access = free }}

Albumin is pronounced {{IPAc-en|ˈ|æ|l|b|j|ʊ|m|ɪ|n}}; formed from Latin: albumen{{cite book | chapter = Pliny the Elder, The Natural History | first = John | last = Bostock | name-list-style = vanc | title = Historia Naturalis 28, 6, 18 | chapter-url = https://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.02.0137 }} "egg white", itself derived from the latin albus: white.

• Cohn process (human serum albumin purification method)
• Serum albumin
• Bovine serum albumin
• Human serum albumin

{{InterPro content|IPR014760}}

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{{EB1911 poster|Albumin}}

• {{MeshName|Albumins}}
• [http://www.albumin.org/ The Albumin website]
• [https://web.archive.org/web/20110807233152/http://albumin.althotas.com/ Albumin binding prediction]
• [https://www.ebi.ac.uk/pdbe/pdbe-kb/proteins/P02768 PDBe-KB] provides an overview of all the structure information available in the PDB for Human Serum albumin.

{{Protein topics}}

{{Albumins}}

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Category:Blood proteins

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