The enzymology of sulfur activation during thiamin and biotin biosynthesis. |
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Authors: | T P Begley J Xi C Kinsland S Taylor F McLafferty |
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Institution: | Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA. tpb2@cornell.edu. |
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Abstract: | The thiamin and biotin biosynthetic pathways utilize elaborate strategies for the transfer of sulfur from cysteine to cofactor precursors. For thiamin, the sulfur atom of cysteine is transferred to a 66-amino-acid peptide (ThiS) to form a carboxy-terminal thiocarboxylate group. This sulfur transfer requires three enzymes and proceeds via a ThiS-acyladenylate intermediate. The biotin synthase Fe-S cluster functions as the immediate sulfur donor for biotin formation. C-S bond formation proceeds via radical intermediates that are generated by hydrogen atom transfer from dethiobiotin to the adenosyl radical. This radical is formed by the reductive cleavage of S-adenosylmethionine by the reduced Fe-S cluster of biotin synthase. |
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