Albumin

For other uses, see Albumin (disambiguation).

Albumin (Latin: albus, white) refers generally to any protein with water solubility, which is moderately soluble in concentrated salt solutions, and experiences heat coagulation (protein denaturation). Substances containing albumin, such as egg white, are called albuminoids.

Types

Serum albumin

The most well-known type of albumin is the serum albumin in the blood.

Serum albumin is the most abundant blood plasma protein and is produced in the liver and forms a large proportion of all plasma protein. The human version is human serum albumin, and it normally constitutes about 70% of human plasma protein; all other proteins present in blood plasma are referred to collectively as globulins.

Serum albumins are important in regulating blood volume by maintaining the osmotic pressure of the blood compartment. They also serve as carriers for molecules of low water solubility, including lipid soluble hormones, bile salts, bilirubin, free fatty acids (apoprotein), calcium, iron (transferrin), and some drugs. Competition between drugs for albumin binding sites may cause drug interaction by increasing the free fraction of one of the drugs, thereby affecting potency.

Specific types include:

• human serum albumin
• bovine serum albumin (cattle serum albumin) or BSA, often used in medical and molecular biology labs.

Low albumin (hypoalbuminaemia) may be caused by liver disease, nephrotic syndrome, burns, protein-losing enteropathy, malabsorption, malnutrition, late pregnancy, artefact, posture, genetic variations and malignancy.

High albumin is almost always caused by dehydration. In some cases of retinol (Vitamin A) deficiency the albumin level can become raised to borderline High-normal values. This is because retinol causes cells to swell with water (this is also the reason too much Vitamin A is toxic)

Normal range of human serum albumin in adults (> 3 y.o.) is 3.5 to 5 g/dL. For children less than three years of age, the normal range is broader, 2.5-5.5 g/dL.

Other types

Other types include the storage protein ovalbumin in egg white, and different storage albumins in the seeds of some plants. Note that albumin is spelled with an "i" while "albumen" with an "e" is the white of an egg.

External links

• Albumins at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
• The Albumin website

See also

• Cohn process (human serum albumin purification method)