Tellurocysteine (in some publications referred to as Te-Cys) is an

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...

with the formula . It is the heavy analogue of

serine Serine (symbol Ser or S) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α- amino group (which is in the protonated − form under biological conditions), a carboxyl group (which is in the deprotonated − ...

cysteine Cysteine (; symbol Cys or C) is a semiessential proteinogenic amino acid with the chemical formula, formula . The thiol side chain in cysteine enables the formation of Disulfide, disulfide bonds, and often participates in enzymatic reactions as ...

, and

selenocysteine Selenocysteine (symbol Sec or U, in older publications also as Se-Cys) is the 21st proteinogenic amino acid. Selenoproteins contain selenocysteine residues. Selenocysteine is an analogue of the more common cysteine with selenium in place of the ...

Tellurol Tellurols are analogues of alcohol (chemistry), alcohols and phenols where tellurium replaces oxygen. Tellurols, selenols, and thiols have similar properties, but tellurols are the least stable. Although they are fundamental representatives of orga ...

(RTeH) is a rare and fragile functional group, especially alkyl derivatives. The C-Te bond (200 kJ/mol) is weak compared to 234 kJ/mol for the C-Se bond. These factors combine to make tellurocysteine very labile. Even selenocysteine occurs only rarely in nature. Instead of tellurocysteine, tellurocystine is generally isolated instead. Tellurocystine has the formula , with a central Te-Te bond. : Tellurocystine2

Properties

The fungus ''

Aspergillus fumigatus ''Aspergillus fumigatus'' is a species of fungus in the genus ''Aspergillus'', and is one of the most common ''Aspergillus'' species to cause disease in individuals with an immunodeficiency. ''Aspergillus fumigatus'', a saprotroph widespread in ...

'' is capable of incorporating tellurocysteine (and telluromethionine) into proteins when grown in appropriate media. When incorporated into

glutathione transferase Glutathione ''S''-transferases (GSTs), previously known as ligandins, are a family of eukaryotic and prokaryotic phase II metabolic isozymes best known for their ability to catalyze the conjugation of the reduced form of glutathione (GSH) to x ...

, tellurocysteine efficiently inhibits

aminoacylation Aminoacylation is the process of adding an aminoacyl group to a compound. See also * Acylation * tRNA aminoacylation * Transfer RNA-like structures References Organic reactions {{Reaction-stub ...

and increases the efficiency of

glutathione peroxidase Glutathione peroxidase (GPx) () is the general name of an enzyme family with peroxidase activity whose main biological role is to protect the organism from oxidative damage. The biochemical function of glutathione peroxidase is to reduce lipid ...

Synthesis

L-Tellurocystine has been prepared in low yield from a protected form of 3-iodo

alanine Alanine (symbol Ala or A), or α-alanine, is an α-amino acid that is used in the biosynthesis of proteins. It contains an amine group and a carboxylic acid group, both attached to the central carbon atom which also carries a methyl group sid ...

. Thus, methyl (2''R'')-2- ''tert''-butoxycarbonyl)amino3-iodopropionate reacts with lithium telluride to produce tellurocystine.

References

{{Reflist Alpha-Amino acids Organotellurium compounds