Selenocysteine

Description

Selenocysteine is often called the 21st essential (protein-forming) amino acid. It is found in countless species of all domains of life. Much research has been reported on the biochemistry of selenocysteine in the North American plant Astragalus bisulcatus.
Scientists long believed that fungi were an exception to the broad prevalence of selenocysteine in life forms. But recently, Vadim N. Gladyshev, Marco Mariotti, and co-workers at Harvard Medical School (Boston) found selenocysteine-containing proteins in three fungus phyla. A few fungal genes that contain selenoproteins behave similarly to those in other organisms; but the mechanisms and purposes of other fungal “selenogenes” are as yet unknown.
Selenium’s wealth of natural and synthetic isotopes makes radiolabeled selenocysteine (Sec) a valuable tool in analytical chemistry and biochemistry. Specifically, 73Se-Sec is used in positron emission tomography (PET); 75Se-Sec in protein X-ray crystallography; and 77Se-Sec in high-resolution nuclear magnetic resonance (NMR) spectroscopy.

The Uses of Selenocysteine

L-Selenocysteine is used in the modulation of oxidative stress through detoxification of biological oxidants as well as repair of oxidized residues.

Definition

ChEBI: The L-enantiomer of selenocysteine.