UDP-(5F)-GlcNAc Acts as a Slow-Binding Inhibitor of MshA, a Retaining Glycosyltransferase
UDP-(5F)-GlcNAc Acts as a Slow-Binding Inhibitor of MshA, a Retaining Glycosyltransferase
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DOI：
10.1021/ja101231a
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发表时间：
2010-05-19
影响因子：
15
通讯作者：
Blanchard, John S.
中科院分区：
文献类型：
--
作者：
Frantom, Patrick A.;Coward, James K.;Blanchard, John S.
糖基转移酶在多种细胞途径中发挥着重要作用。尽管它们参与了许多治疗相关的途径，但关于如何有效地抑制这类酶的信息很少。在这里，我们报道了UDP-(5F)-GlcNAc作为谷氨酸棒杆菌保留糖基转移酶MSHA的慢结合竞争性抑制剂(K(I)=1.6mM)。动力学数据符合单步抑制机理，其平衡比催化慢。我们认为这是第一个报道的糖基转移酶家族的慢效抑制剂。氟取代底物对酶的有效抑制与氧碳正离子过渡态结构的参与是一致的，这是先前提出的这一家族酶的结构。此外，尽管GT-B酶家族的几个成员，包括MSHA，已经被证明在UDP-GlcNAc结合时经历了构象变化，但动力学数据与两步抑制机制不一致。这表明，该酶的其他构象可能对设计针对GT-B糖基转移酶大家族的抑制剂有用。
Glycosyltransferase enzymes play important roles in numerous cellular pathways. Despite their participation in many therapeutically relevant pathways, there is a paucity of information on how to effectively inhibit this class of enzymes. Here we report that UDP-(5F)-GlcNAc acts as a slow-binding, competitive inhibitor of the retaining glycosyltransferase MshA from Corynebacterium glutamicum (K(i) = 1.6 mu M). The kinetic data are consistent with a single-step inhibition mechanism whose equilibration is slow relative to catalysis. We believe that this is the first slow-onset inhibitor to be reported for the glycosyltransferase family of enzymes. The potent inhibition of the enzyme by the fluoro-substituted substrate is consistent with the involvement of an oxocarbenium transition-state structure, which has been previously proposed for this family of enzymes. Additionally, although several members of the GT-B enzyme family, including MshA, have been shown to undergo a conformational change upon UDP-GlcNAc binding, the kinetic data are inconsistent with a two-step inhibition mechanism. This suggests that there may be other conformations of the enzyme that are useful for the design of inhibitors against the large family of GT-B glycosyltransferase enzymes.