Evans Charles, Bogan Katrina L, Song Peng, Burant Charles F, Kennedy Robert T, Brenner Charles
Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA.
BMC Chem Biol. 2010 Feb 22;10:2. doi: 10.1186/1472-6769-10-2.
NAD+ is a coenzyme for hydride transfer enzymes and a substrate for sirtuins and other NAD+-dependent ADPribose transfer enzymes. In wild-type Saccharomyces cerevisiae, calorie restriction accomplished by glucose limitation extends replicative lifespan in a manner that depends on Sir2 and the NAD+ salvage enzymes, nicotinic acid phosphoribosyl transferase and nicotinamidase. Though alterations in the NAD+ to nicotinamide ratio and the NAD+ to NADH ratio are anticipated by models to account for the effects of calorie restriction, the nature of a putative change in NAD+ metabolism requires analytical definition and quantification of the key metabolites.
Hydrophilic interaction chromatography followed by tandem electrospray mass spectrometry were used to identify the 12 compounds that constitute the core NAD+ metabolome and 6 related nucleosides and nucleotides. Whereas yeast extract and nicotinic acid increase net NAD+ synthesis in a manner that can account for extended lifespan, glucose restriction does not alter NAD+ or nicotinamide levels in ways that would increase Sir2 activity.
The results constrain the possible mechanisms by which calorie restriction may regulate Sir2 and suggest that provision of vitamins and calorie restriction extend lifespan by different mechanisms.
NAD⁺是氢化物转移酶的辅酶，也是去乙酰化酶和其他NAD⁺依赖性ADP核糖转移酶的底物。在野生型酿酒酵母中，通过葡萄糖限制实现的热量限制以一种依赖Sir2以及NAD⁺补救酶、烟酸磷酸核糖基转移酶和烟酰胺酶的方式延长复制寿命。尽管模型预测NAD⁺与烟酰胺的比例以及NAD⁺与NADH的比例变化可解释热量限制的影响，但NAD⁺代谢假定变化的本质需要对关键代谢物进行分析定义和定量。
采用亲水相互作用色谱法结合串联电喷雾质谱法鉴定了构成核心NAD⁺代谢组的12种化合物以及6种相关核苷和核苷酸。酵母提取物和烟酸以一种可解释寿命延长的方式增加NAD⁺的净合成，而葡萄糖限制并不会以增加Sir2活性的方式改变NAD⁺或烟酰胺水平。
这些结果限制了热量限制可能调节Sir2的潜在机制，并表明提供维生素和热量限制通过不同机制延长寿命。
