Serum albumin

Serum albumin, often referred to simply as blood albumin, is an is_associated_with::albumin (a type of globular is_associated_with::protein) found in vertebrate is_associated_with::blood. is_associated_with::Human serum albumin is encoded by the ALB is_associated_with::gene. Other is_associated_with::mammalian forms, such as is_associated_with::bovine serum albumin, are chemically similar.

Serum albumin is produced by the is_associated_with::liver, occurs dissolved in is_associated_with::blood plasma and is the most abundant is_associated_with::blood protein in is_associated_with::mammals. Albumin is essential for maintaining the is_associated_with::oncotic pressure needed for proper distribution of is_associated_with::body fluids between blood vessels and body tissues; without albumin, the high pressure in the blood vessels would force more fluids out into the tissues. It also acts as a plasma carrier by non-specifically binding several is_associated_with::hydrophobic is_associated_with::steroid hormones and as a transport protein for is_associated_with::hemin and is_associated_with::fatty acids. Too much or too little circulating serum albumin may be harmful.

Function
Albumin functions primarily as a carrier protein for is_associated_with::steroids, is_associated_with::fatty acids, and is_associated_with::thyroid hormones in the blood and plays a major role in stabilizing extracellular fluid volume by contributing to is_associated_with::oncotic pressure (known also as colloid osmotic pressure) of plasma.

Because smaller animals (for example is_associated_with::rats) function at a lower is_associated_with::blood pressure, they need less oncotic pressure to balance this, and thus need less albumin to maintain proper fluid distribution.

Synthesis
Albumin is synthesized in the is_associated_with::liver as preproalbumin which has an N-terminal peptide that is removed before the nascent protein is released from the rough is_associated_with::endoplasmic reticulum. The product, proalbumin, is in turn cleaved in the Golgi vesicles to produce the secreted albumin.

Properties
Albumin is a globular, water-soluble, un-glycosylated serum protein of approximate molecular weight of 65,000 Daltons.

Albumin (when ionized in water at pH 7.4, as found in the body) is negatively charged. The is_associated_with::glomerular basement membrane is also negatively charged in the body; some studies suggest that this prevents the filtration of albumin in the urine. According to this theory, that charge plays a major role in the selective exclusion of albumin from the glomerular filtrate. A defect in this property results in is_associated_with::nephrotic syndrome leading to albumin loss in the urine. Nephrotic syndrome patients are sometimes given albumin to replace the lost albumin.

Structure
The general structure of albumin is characterized by several long α helices, this allows it to maintain a relatively static shape, something essential for regulating blood pressure.

Serum albumin contains eleven distinct binding domains for hydrophobic compounds. One is_associated_with::hemin and six long-chain is_associated_with::fatty acids can bind to serum albumin at the same time.

Types
Serum albumin is widely distributed in mammals.
 * The human version is is_associated_with::human serum albumin.
 * is_associated_with::Bovine serum albumin, or BSA, is commonly used in immunodiagnostic procedures, clinical chemistry reagents, cell culture media, protein chemistry research (including venom toxicity), and is_associated_with::molecular biology laboratories (usually to leverage its non-specific protein binding properties).