期刊
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
卷 54, 期 3, 页码 860-863出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.201409540
关键词
biosynthesis; carbohydrates; enzyme catalysis; radical reactions; S-adenosylmethionine
资金
- National Institutes of Health [GM035906]
- Welch Foundation [F-1511]
DesII is a radical S-adenosylmethionine (SAM) enzyme that catalyzes the C4-deamination of TDP-4-amino-4,6-dideoxyglucose through a C3 radical intermediate. However, if the C4 amino group is replaced with a hydroxy group (to give TDP-quinovose), the hydroxy group at C3 is oxidized to a ketone with no C4-dehydration. It is hypothesized that hyperconjugation between the C4 C-N/O bond and the partially filled p orbital at C3 of the radical intermediate modulates the degree to which elimination competes with dehydrogenation. To investigate this hypothesis, the reaction of DesII with the C4-epimer of TDP-quinovose (TDP-fucose) was examined. The reaction primarily results in the formation of TDP-6-deoxygulose and likely regeneration of TDP-fucose. The remainder of the substrate radical partitions roughly equally between C3-dehydrogenation and C4-dehydration. Thus, changing the stereochemistry at C4 permits a more balanced competition between elimination and dehydrogenation.
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