The origin of the sulfur atom in thiamine |
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Authors: | Edward Bellion David H Kirkley |
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Institution: | Department of Chemistry, The University of Texas at Arlington, Arlington, Texas 76019, U.S.A. |
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Abstract: | The mode of biosynthesis of the thiazole moiety of thiamine, 4-methyl-5β-hydroxyethyl thiazole (MHET) was studied using Salmonella typhimurium as test organism. It was shown by isotope incorporation experiments, that the sulfur atom, but not carbon-3, of cysteine is incorporated into MHET, indicating a separation of the sulfur atom of cysteine from the carbon chain during incorporation. Isotope competition experiments revealed that the incorporation of 35S]cysteine is not significantly diluted by the presence of methionine, homocysteine, and glutathione. No incorporation of label from 14C]glutamate and 14C]formate was observed, leaving the origin of the five-carbon unit still in doubt. |
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