Mechanism of sirtuin inhibition by nicotinamide:: Altering the NAD+ cosubstrate specificity of a Sir2 enzyme
Mechanism of sirtuin inhibition by nicotinamide:: Altering the NAD+ cosubstrate specificity of a Sir2 enzyme
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DOI：
10.1016/j.molcel.2005.02.022
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发表时间：
2005-03-18
期刊：
影响因子：
16
通讯作者：
Wolberger, C
中科院分区：
文献类型：
--
作者：
Avalos, JL;Bever, KM;Wolberger, C
Sir2酶形成多种生物过程所需的一类独特的NAD+依赖性脱乙酰酶，包括转录沉默、细胞凋亡调节、脂肪动员和寿命调节。Sir2活性受烟酰胺调节，烟酰胺是一种非竞争性抑制剂，以脱乙酰为代价促进碱交换反应。为了阐明烟酰胺抑制的机制，我们确定了含有烟酰胺的Sir2酶的三元复合物结构。结构显示游离烟酰胺结合在参与NAD（+）结合和催化的保守口袋中。基于我们的结构，我们设计了一个突变体，通过使用烟酸腺嘌呤二核苷酸（NAAD）作为共底物脱乙酰肽，并被烟酸抑制。改变特异性酶的特征确定Sir2酶含有参与催化和烟酰胺调节的单个位点，并提供了对Sir2催化机制的额外见解。
Sir2 enzymes form a unique class of NAD+-dependent deacetylases required for diverse biological processes, including transcriptional silencing, regulation of apoptosis, fat mobilization, and lifespan regulation. Sir2 activity is regulated by nicotinamide, a noncompetitive inhibitor that promotes a base-exchange reaction at the expense of deacetylation. To elucidate the mechanism of nicotinamide inhibition, we determined ternary complex structures of Sir2 enzymes containing nicotinamide. The structures show that free nicotinamide binds in a conserved pocket that participates in NAD(+) binding and catalysis. Based on our structures, we engineered a mutant that deacetylates peptides by using nicotinic acid adenine dinucleotide (NAAD) as a cosubstrate and is inhibited by nicotinic acid. The characteristics of the altered specificity enzyme establish that Sir2 enzymes contain a single site that participates in catalysis and nicotinamide regulation and provides additional insights into the Sir2 catalytic mechanism.