Tellurocysteine


Tellurocysteine is an amino acid analogous to serine, cysteine and selenocysteine with tellurium in place of oxygen, sulfur or selenium in its side chain. It is not naturally found in organisms.

Properties

Perhaps due to its low bond energy with carbon, tellurocysteine is not present in any known natural organisms and is hence relatively understudied in comparison to selenocysteine. Despite so, certain organisms such as fungi Aspergillus fumigatus is capable of incorporating tellurocysteine and telluromethionine into amino acids and proteins when exposed to a sulfur-free environment.
It has been observed that when incorporated into glutathione transferase, tellurocysteine efficiently inhibited aminoacylation and increased the efficiency of glutathione peroxidase.

Synthesis

L-Tellurocysteine has been prepared from elemental tellurium by first reacting it with methyl -2--3-iodopropionate in a tetrahydrofuran solvent with presence of lithium triethylborohydride, yielding a red oil which is acidified and treated with alkali before a treatment with citric acid to set its pH to 4.0, resulting in an orange solid after filtering and drying.