期刊
BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS
卷 1824, 期 11, 页码 1213-1222出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbapap.2012.01.010
关键词
Enzyme mechanism; Radical enzyme; Iron-sulfur cluster; Biotin biosynthesis; Cofactor biosynthesis
资金
- National Science Foundation [MCB 09-23829]
- Direct For Biological Sciences
- Div Of Molecular and Cellular Bioscience [0923829] Funding Source: National Science Foundation
The enzyme cofactor and essential vitamin biotin is biosynthesized in bacteria, fungi, and plants through a pathway that culminates with the addition of a sulfur atom to generate the five-membered thiophane ring. The immediate precursor, dethiobiotin, has methylene and methyl groups at the C6 and C9 positions, respectively, and formation of a thioether bridging these carbon atoms requires cleavage of unactivated C-H bonds. Biotin synthase is an S-adenosyl-L-methionine (SAM or AdoMet) radical enzyme that catalyzes reduction of the AdoMet sulfonium to produce 5'-deoxyadenosyl radicals, high-energy carbon radicals that can directly abstract hydrogen atoms from dethiobiotin. The available experimental and structural data suggest that a [2Fe-2S](2+) cluster bound deep within biotin synthase provides a sulfur atom that is added to dethiobiotin in a stepwise reaction, first at the C9 position to generate 9-mercaptodethiobiotin, and then at the C6 position to close the thiophane ring. The formation of sulfur-containing biomolecules through a radical reaction involving an iron-sulfur cluster is an unprecedented reaction in biochemistry; however, recent enzyme discoveries suggest that radical sulfur insertion reactions may be a distinct subgroup within the burgeoning Radical SAM superfamily. This article is part of a Special Issue entitled: Radical SAM enzymes and Radical Enzymology. (C) 2012 Elsevier B.V. All rights reserved.
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