Human serum albumin
- OMIM: 103600
- UniProt: P02768
- MGI: 87991
- CAS Number: 9048-49-1
The Human albumin is the human form of albumin. Is a globular, blood occurring protein. Albumin serves to maintain the oncotic Drucks. It is reduced in liver disease, among others. In healthy people, there is a concentration of 35 to 53 g / l in the serum. Mutations in the ALB gene responsible for a rare hereditary form of hyperthyroxinemia. Very rarely, the protein may be completely absent.
Properties
Albumin has a molecular weight of about 66,470 Da, and is elliptical in shape. It consists of 585 amino acids, many of which contain sulfur. It is water-soluble, the water binding capacity is about 18 mL / g The isoelectric point is at pH 4.6. Albumin is an ampholyte, i.e., in contrast to other colloids, crystalloids or may bind to both anions and cations reversibly.
Average a person has (70 kg) in healthy condition 250-320 g albumin. 40 % of which are located within the blood vessels in the blood plasma solved, 60 % outside of the vessels in the tissue. In addition to the albumins still other proteins are globulins in the blood. Although albumins represent the smaller protein locations of the two plasma proteins, they are quantitatively with 60 % ( 3.5-4.5 g / dl ) in the majority, globulins account for only 40%.
Biosynthesis
Albumin is the gene product of the ALB gene, the gene locus is located on chromosome 4 q13.3. The synthesis of albumin takes place in the liver at an average synthesis rate of 0.2 g albumin / kg of body weight per day. The of the liver cells (hepatocytes ) produced Preproalbumin is modified post-translationally in the rough endoplasmic reticulum. By the removal of amino acids at the N-terminus produced proalbumin. The proalbumin is ultimately converted into the Golgi vesicles to albumin. The degradation proceeds via the kidneys, the gastrointestinal tract happening swiftly and successfully in the tissue cells of the liver.
The Chinese researchers Daichang Yang succeeded in 2011 to produce human albumin using genetically modified rice plants.
Biological Function
Maintenance of colloid osmotic pressure
By albumin in the blood vessels binds water in itself, it prevents it from escaping into the spaces between the cells and thus the tissue. Since albumins are responsible for 80 percent of the colloid osmotic pressure of the plasma, can you lack the pressure drop automatically and leads to edema ( fluid in the tissue ).
Hydrophobic substances such as fatty acids, bilirubin, trace elements, certain vitamins, hormones, cations ( Mg2 , Ca2 ) and drugs could not be transported without being bound to albumin in the blood. Up to 20-25 bilirubin molecules, 9 stearic acid molecules or 5 salicylic acid molecules, a single albumin molecule reversibly bind to itself.
Contribution to the buffer capacity of the blood
Due to their properties ampholytics assets albumins by
Disorders of albumin household
It is produced in the liver, which is important in the context of various diseases. In cirrhosis of the liver (eg, due to chronic alcohol abuse) the institution's capacity to synthesize albumin is limited ( hypoalbuminemia ), resulting in edema and ascites due to the decreased colloid osmotic pressure of blood plasma. Similarly, in chronic malnutrition, as the albumin formation is also reduced by the lack of protein and amino acid intake, and serum albumin in addition to other protein reserves, such as muscle tissue is broken down. A non-pathological loss of albumin, the hypoalbuminemia with albuminuria of pregnancy dar.