Tellurocysteine Explained

Tellurocysteine (in some publications referred to as Te-Cys) is an amino acid with the formula . It is the heavy analogue of serine, cysteine, and selenocysteine. Tellurol (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.^[1] These factors combine to make tellurocysteine very labile. Even selenocysteine occurs only rarely in nature.^[2] Instead of tellurocysteine, tellurocystine is generally isolated instead. Tellurocystine has the formula, with a central Te-Te bond.

Properties

The fungus Aspergillus fumigatus is capable of incorporating tellurocysteine (and telluromethionine) into proteins when grown in appropriate media.^[3]

When incorporated into glutathione transferase, tellurocysteine efficiently inhibits aminoacylation and increases the efficiency of glutathione peroxidase.^[4]

Synthesis

L-Tellurocystine has been prepared in low yield from a protected form of 3-iodoalanine. Thus, methyl (2R)-2-[(''tert''-butoxycarbonyl)amino]-3-iodopropionate reacts with lithium telluride to produce tellurocystine.^[5]

Notes and References

1. Chivers. Tristram. Laitinen. Risto S.. Tellurium: a maverick among the chalcogens. Chemical Society Reviews. 23 March 2015. 44. 7. 1725–1739. 10.1039/C4CS00434E. 25692398. en. 1460-4744.
2. Book: Advances in Microbial Physiology. 2007. Academic Press. 9780080560649. 4. en.
3. Ramadan. ShadiaE.. Razak. A.A.. Ragab. A.M.. El-Meleigy. M.. Incorporation of tellurium into amino acids and proteins in a tellurium-tolerant fungi. Biological Trace Element Research. 1 June 1989. 20. 3. 225–232. 10.1007/BF02917437. 2484755. 9439946. English. 0163-4984.
4. Liu. Xiaoman. Silks. Louis A.. Liu. Cuiping. Ollivault-Shiflett. Morgane. Huang. Xin. Li. Jing. Luo. Guimin. Hou. Ya-Ming. Liu. Junqiu. Shen. Jiacong. Incorporation of Tellurocysteine into Glutathione Transferase Generates High Glutathione Peroxidase Efficiency. Angewandte Chemie International Edition. 2 March 2009. 48. 11. 2020–2023. 10.1002/anie.200805365. 19199319.
5. Stocking. Emily M.. Schwarz. Jessie N.. Senn. Hans. Salzmann. Michael. Silks. Louis A.. Synthesis of L-selenocystine,L-[77Se]selenocystine and L-tellurocystine. Journal of the Chemical Society, Perkin Transactions 1. 1 January 1997. 16. 2443–2448. 10.1039/A600180G. en. 1364-5463.