What are the benefits of albumin to human body?

Albumin (also known as albumin, Alb) is synthesized by liver parenchyma cells, and its half-life in plasma is about 15- 19 days. It is the most abundant protein in plasma, accounting for 40%-60% of total plasma protein. Although its synthesis speed is influenced by the content of protein in food, it is mainly regulated by the level of albumin in plasma. Albumin is not stored in hepatocytes, and all extracellular fluids contain trace albumin. Regarding the filtration of albumin in glomerulus, it is generally believed that the amount of albumin is very small under normal circumstances, which is about 0.04% of albumin in plasma. According to this calculation, the amount of albumin excreted from glomerular filtrate every day can reach 3.6g, which is 30-40 times that of the final urine. It can be seen that most albumin in the filtrate can be reabsorbed by renal tubules. The experiment confirmed that albumin was absorbed by the proximal convoluted tubule and degraded into small molecular fragments by the hydrolytic enzymes in lysosomes in the tubule cells, which entered the blood circulation. Albumin can be absorbed by cells in different tissues, and its amino acids can be used for tissue repair.

The molecular structure of albumin is illustrated in 1975. It is a single-chain polypeptide with 585 amino acid residues, with a molecular weight of 66,458, with 17 disulfide bonds in the molecule and no sugar content. In the environment of body fluid pH7.4, albumin is a negative ion, and each molecule can carry more than 200 negative charges. It is the main carrier in plasma, and many substances with poor water solubility can be transported by combining with albumin. These substances include bilirubin, long-chain fatty acids (each molecule can bind 4-6 molecules), bile salts, prostaglandins, steroid hormones, metal ions (such as Cu2+, Ni2+, Ca2+) drugs (such as aspirin and penicillin).

When combined with albumin, active hormones or drugs can be regarded as their stored form without showing their activity. Because of the reversibility and dynamic balance of this combination, it is of great significance in regulating the metabolism of these hormones and drugs.