Structural characterization of a human cytosolic NMN/NaMN adenylyltransferase and implication in human NAD biosynthesis
Structural characterization of a human cytosolic NMN/NaMN adenylyltransferase and implication in human NAD biosynthesis
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DOI：
10.1074/jbc.m300073200
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发表时间：
2003-04-11
影响因子：
4.8
通讯作者：
Zhang, H
中科院分区：
文献类型：
--
作者：
Zhang, XJ;Kurnasov, OV;Zhang, H
吡啶二核苷酸(NAD和NADP)是广泛存在的辅因子，参与了数百个氧化还原反应，对所有活细胞的能量传递和代谢都是必不可少的。此外，NAD也是许多核蛋白ADP核糖化的底物，参与基因沉默调控的沉默信息调节因子2(Sir2)样组蛋白去乙酰基酶，以及依赖环状ADP核糖(CADPR)的钙信号转导。吡啶核苷酸腺苷转移酶(PNAT)是NAD生物合成途径中不可缺少的中心酶，催化吡啶单核苷酸(NMN或NaMN)与ATP的AMP部分缩合形成NAD(或NaAD)。在这里，我们报道了一种新的人类PNAT(hsPNAT-3)的鉴定和结构特征，它位于细胞质和线粒体中。它的亚细胞定位和组织分布与以前发现的人类核PNAT-1和PNAT-2不同。对PNAT-3的载脂蛋白及其与底物(S)或产物的络合物进行了详细的结构分析，揭示了该酶的催化机理。对人PNAT-3胞浆的鉴定提供了令人信服的证据，表明NAD生物合成途径的最后步骤可能存在于哺乳动物的细胞质和线粒体中，可能有助于它们的NAD/NADP池。
Pyridine dinucleotides (NAD and NADP) are ubiquitous cofactors involved in hundreds of redox reactions essential for the energy transduction and metabolism in all living cells. In addition, NAD also serves as a substrate for ADP-ribosylation of a number of nuclear proteins, for silent information regulator 2 (Sir2)-like histone deacetylase that is involved in gene silencing regulation, and for cyclic ADP ribose (cADPR)-dependent Ca2+ signaling. Pyridine nucleotide adenylyltransferase (PNAT) is an indispensable central enzyme in the NAD biosynthesis pathways catalyzing the condensation of pyridine mononucleotide (NMN or NaMN) with the AMP moiety of ATP to form NAD (or NaAD). Here we report the identification and structural characterization of a novel human PNAT (hsPNAT-3) that is located in the cytoplasm and mitochondria. Its subcellular localization and tissue distribution are distinct from the previously identified human nuclear PNAT-1 and PNAT-2. Detailed structural analysis of PNAT-3 in its apo form and in complex with its substrate(s) or product revealed the catalytic mechanism of the enzyme. The characterization of the cytosolic human PNAT-3 provided compelling evidence that the final steps of NAD biosynthesis pathways may exist in mammalian cytoplasm and mitochondria, potentially contributing to their NAD/NADP` pool.