Structural basis for the mechanistic understanding of human CD38-controlled multiple catalysis
Structural basis for the mechanistic understanding of human CD38-controlled multiple catalysis
复制标题
DOI：
10.1074/jbc.m606365200
复制
发表时间：
2006-10-27
影响因子：
4.8
通讯作者：
Hao, Quan
中科院分区：
文献类型：
--
作者：
Liu, Qun;Kriksunov, Irina A.;Hao, Quan
在烟酰胺腺嘌呤二核苷酸（NAD(+)）上的烟酰胺-糖苷键的酶切被认为是通过氧羰基离子样过渡态进行的。由于离子中间体的不稳定性，目前还没有关于这种瞬态反应物质的结构报道。人CD38是一种能利用NAD（+）合成两种钙动员分子的外酶。通过使用NAD（+）和替代底物NGD(+)，我们捕获并确定了酶与中间体、底物和反应途径中的产物络合的晶体结构。我们的研究结果表明中间体是通过与催化残基Glu（226）的极性相互作用而不是通过共价键来稳定的。Glu（226）与底物2',3'-OH基团之间的极性相互作用是引发催化的必要条件。Ser（193）被证明在催化过程中具有调节作用，并可能参与中间稳定。此外，观察到adp -核糖（通过产物的重定向）或gdp -核糖（通过形成共价连接的gdp -核糖二聚体）的产物抑制作用。这些结构数据为理解多重催化和药物设计提供了线索。
The enzymatic cleavage of the nicotinamide-glycosidic bond on nicotinamide adenine dinucleotide (NAD(+)) has been proposed to go through an oxocarbenium ion-like transition state. Because of the instability of the ionic intermediate, there has been no structural report on such a transient reactive species. Human CD38 is an ectoenzyme that can use NAD(+) to synthesize two calcium-mobilizing molecules. By using NAD(+) and a surrogate substrate, NGD(+), we captured and determined crystal structures of the enzyme complexed with an intermediate, a substrate, and a product along the reaction pathway. Our results showed that the intermediate is stabilized by polar interactions with the catalytic residue Glu(226) rather than by a covalent linkage. The polar interactions between Glu(226) and the substrate 2', 3'-OH groups are essential for initiating catalysis. Ser(193) was demonstrated to have a regulative role during catalysis and is likely to be involved in intermediate stabilization. In addition, a product inhibition effect by ADP-ribose (through the reorientation of the product) or GDP-ribose (through the formation of a covalently linked GDP-ribose dimer) was observed. These structural data provide insights into the understanding of multiple catalysis and clues for drug design.