Sandbox reserve166
From Proteopedia
Contents |
Background
Albumin is a protein that is water soluable, can be semi-soluable in salt concentrations and can be coagulated by heat. Serum albumin is a transport blood protein found in the blood plasma. There are other types of serum transport proteins such as: alpha - fetoprotein, vitamin -D binding protein, and afamin.
What it is and were and how its made
Serum albumin is a blood prtein. Albumin makes up half of the blood serum. The other half is The gene for albumin is located on chromosome 4 and it is 16,961 nucleotides long from the putative "cap" site to the first poly (A) addition site. The gene is split into 15 exons that are symetrically placed within 3 domains.
Albumin synthesis begins in the nucleus, where genes are transcribed into messenger ribonucleic acid (mRNA). The mRNA is secreted into the cytoplasm, where it is bound to ribosomes, forming polysomes that synthesize preproalbumin. Preproalbumin is an albumin molecule with a 24 amino acid extension at the N terminal peptide. The amino acid extension signals insertion of preproalbumin into the membrane of the endoplasmic reticulum. Once inside the lumen of the endoplasmic reticulum, the leading 18 amino acids of this extension are cleaved, leaving proalbumin (albumin with the remaining extension of 6 amino acids). Proalbumin is the principal intracellular form of albumin. Proalbumin is exported to the Golgi apparatus, where the extension of 6 amino acids is removed prior to secretion of albumin by the hepatocyte. Once synthesized, albumin is secreted immediately; it is not stored in the liver.
What it binds to, and its main function:
It binds to water,cations ( such as Ca2+, Na+ and K+), fatty acids,hormones,bilirubin and certain drugs (see below). Its main function is to regulate colloidal osmotic pressure of blood. When serum albumin can no longer sustain colloidal osmotic pressure to counterbalance hydrostatic pressure, edema can develop. Albumin transports various substances, including bilirubin, fatty acids, metals, ions, hormones, and exogenous drugs.
Sturcture
Role in Disease
Low levels of serum albumin which is called hypoalbuminemia, can be caused by liver disease, nephrotic syndrom, burns, malabsorption, malnutrition. One of the consequences of hypoalbuminemia is that drugs that are usually bound to the albumin protein are free in the plasma, which can cause higher drug levels and or faster liver metabolism. High levels of serum albumin which is called hyperalbuminemia, is usually caused by dehydration. Retinol ( vitamin A) deficiancy can cause cells to swell with water, which is why too much vitamin A is toxic.
Interaction with Drugs
Some of the drugs that serum albumin carries are: warfarin, phenobutazone, clofibrate and phenytoin. There can be competition between drugs for albumin binding sites which can attect the potency of that drug.
References
Finfer S, Bellomo R, McEvoy S, Lo SK, Myburgh J, Neal B, et al. Effect of baseline serum albumin concentration on outcome of resuscitation with albumin or saline in patients in intensive care units: analysis of data from the saline versus albumin fluid evaluation (SAFE) study. BMJ. Nov 18 2006;333(7577):1044. [Medline].
