Selenoprotein P

Se is an essential micronutrient, and is incorporated into proteins in the form of selenocysteine. These proteins containing selenocysteine (Sec) are termed selenoproteins.

Selenoprotein P (SeP: the “P” denotes its presence in plasma) is a selenium-rich extracellular protein and is the major selenoprotein in plasma.

All selenoproteins so far reported contain one atom of selenium (Se) as selenocysteine per molecule except SeP, which is thought to contain ten atoms of Se as selenocysteine per molecule. SeP accounts for more than 50% of the selenium content in plasma.

SeP is a potentially multifunctional protein with both enzymatic and Se-transport activities that plays a central role in body Se transport and maintaining tissue Se hierarch.

Research shows that SeP affects Aβ and hyperphosphorylated tau aggregation and toxicity in addition to interacting with redox-active metals in the brain, such as Cu, Fe, and Hg. It is capable of antioxidant enzyme activity and appears to possess signaling functions via neuronal ApoER2.
Selenoprotein P

Selenoproteins

Selenium is an essential micronutrient for man and animals. The role of selenium has been attributed largely to its presence in selenoproteins as the 21st amino acid, selenocysteine.

Selenium is incorporated into proteins in the form of selenocysteine. These proteins containing selenocysteine (Sec) are termed selenoproteins. Selenoproteins are present in all lineages of life (i.e., bacteria, archaea, and eukarya).

Families of selenoproteins include the glutathione peroxidases, the iodothyronine deiodinases and the thioredoxin reductases.

Selenoproteomes among species are generally small; the largest repertoire exists in fish with 30 individual selenoproteins, followed by humans and rodents with 25 and 24 selenoproteins, respectively.

Selenoproteins have biological functions in oxidoreductions, redox signaling, antioxidant defense, thyroid hormone metabolism, and immune responses.

Approximately 10 additional selenoproteins have been identified. One of them, selenoprotein P, is an extracellular protein that contains most of the selenium in plasma. It associates with endothelial cells, probably through its heparin-binding properties.
Selenoproteins