Tellurocysteine

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

Tellurocysteine
Names
IUPAC name
(2R)-2-Amino-3-tellanylpropanoic acid
Other names
Tellurocystine
Identifiers
3D model (JSmol)
ChemSpider
Properties
C3H7NO2Te
Molar mass 216.69 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Properties

Perhaps due to its low bond energy with carbon (200 kJ/mol compared to 234 kJ/mol for selenium, or 272 kJ/mol for sulfur),[1] tellurocysteine is not present in any known natural organisms and is hence relatively understudied in comparison to selenocysteine.[2] 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.[3]

It has been observed that when incorporated into glutathione transferase, tellurocysteine efficiently inhibited aminoacylation and increased the efficiency of glutathione peroxidase.[4]

Synthesis

L-Tellurocysteine has been prepared from elemental tellurium by first reacting it with methyl (2R)-2-[(tert-butoxycarbonyl)amino]-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.[5]

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References
  1. Chivers, Tristram; Laitinen, Risto S. (23 March 2015). "Tellurium: a maverick among the chalcogens". Chemical Society Reviews. 44 (7): 1725–1739. doi:10.1039/C4CS00434E. ISSN 1460-4744. PMID 25692398.
  2. Advances in Microbial Physiology. Academic Press. 2007. p. 4. ISBN 9780080560649.
  3. Ramadan, ShadiaE.; Razak, A.A.; Ragab, A.M.; El-Meleigy, M. (1 June 1989). "Incorporation of tellurium into amino acids and proteins in a tellurium-tolerant fungi". Biological Trace Element Research. 20 (3): 225–232. doi:10.1007/BF02917437. ISSN 0163-4984. PMID 2484755.
  4. Liu, Xiaoman; Silks, Louis A.; Liu, Cuiping; Ollivault-Shiflett, Morgane; Huang, Xin; Li, Jing; Luo, Guimin; Hou, Ya-Ming; Liu, Junqiu; Shen, Jiacong (2 March 2009). "Incorporation of Tellurocysteine into Glutathione Transferase Generates High Glutathione Peroxidase Efficiency". Angewandte Chemie International Edition. 48 (11): 2020–2023. doi:10.1002/anie.200805365. PMID 19199319.
  5. Stocking, Emily M.; Schwarz, Jessie N.; Senn, Hans; Salzmann, Michael; Silks, Louis A. (1 January 1997). "Synthesis of L-selenocystine,L-[77Se]selenocystine andL-tellurocystine". Journal of the Chemical Society, Perkin Transactions 1. 0 (16): 2443–2448. doi:10.1039/A600180G. ISSN 1364-5463.
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