Mechanistic Studies of the Radical<i>S</i>-Adenosylmethionine Enzyme DesII with TDP-<scp>D</scp>-Fucose
作者:Yeonjin Ko、Mark W. Ruszczycky、Sei-Hyun Choi、Hung-wen Liu
DOI:10.1002/anie.201409540
日期:2015.1.12
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 CN/O bond and the partially
DesII 是一种自由基S-腺苷甲硫氨酸 (SAM) 酶,可通过 C3 自由基中间体催化 TDP-4-氨基-4,6-二脱氧葡萄糖的 C4 脱氨基作用。然而,如果 C4 氨基被羟基取代(得到 TDP-奎诺糖),C3 上的羟基会被氧化成酮,而不会发生 C4 脱水。据推测,C4 C - N/O 键和自由基中间体 C3 处部分填充的 p 轨道之间的超共轭调节了消除与脱氢竞争的程度。为了研究这一假设,我们检查了 DesII 与 TDP-奎诺糖 (TDP-岩藻糖) C4-差向异构体的反应。该反应主要导致 TDP-6-脱氧古洛糖的形成,并可能导致 TDP-岩藻糖的再生。底物自由基的其余部分在 C3-脱氢和 C4-脱水之间大致相等地分配。因此,改变 C4 的立体化学可以实现消除和脱氢之间更平衡的竞争。