AMP and GMP Catabolism in Arabidopsis Converge on Xanthosine, Which Is Degraded by a Nucleoside Hydrolase Heterocomplex
AMP and GMP Catabolism in Arabidopsis Converge on Xanthosine, Which Is Degraded by a Nucleoside Hydrolase Heterocomplex
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DOI：
10.1105/tpc.18.00899
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发表时间：
2019-03-01
期刊：
影响因子：
11.6
通讯作者：
Witte, Claus-Peter
中科院分区：
文献类型：
--
作者：
Baccolini, Chiara;Witte, Claus-Peter
植物可以完全分解代谢嘌呤核苷酸。一个确定的中心中间体是嘌呤基黄嘌呤。在目前广泛接受的植物嘌呤核苷酸催化模型中，黄嘌呤可以以各种方式产生，包括肌苷和次黄嘌呤或鸟苷和黄苷作为中间体。在涉及尿酸氧化酶、黄嘌呤脱氢酶、核苷水解酶、鸟苷脱氨酶和次黄嘌呤鸟嘌呤磷酸核糖基转移酶的单个和多个突变体的综合突变体分析中，我们证明了拟南芥中嘌呤核苷酸catenase（拟南芥）主要产生黄苷，但不产生肌苷和次黄嘌呤，并且黄苷来源于鸟苷脱氨基和第二来源，可能是黄苷一磷酸脱磷酸化。已知核苷水解酶1（NSH 1）对于黄苷水解是必需的，但第二种胞质核苷水解酶NSH 2的体内功能尚不清楚。我们证明，NSH1激活NSH2在体外和体内，形成一个复杂的黄嘌呤水解的催化效率几乎两个数量级比单独观察NSH1。值得注意的是，失活的NSH1点突变体可以在体内激活NSH2，完全防止嘌呤核苷在nsh1背景下的积累。我们的数据导致改变模型的嘌呤核苷酸catastrophin，包括一个NSH杂复合物作为一个中心组件。
Plants can fully catabolize purine nucleotides. A firmly established central intermediate is the purine base xanthine. In the current widely accepted model of plant purine nucleotide catabolism, xanthine can be generated in various ways involving either inosine and hypoxanthine or guanosine and xanthosine as intermediates. In a comprehensive mutant analysis involving single and multiple mutants of urate oxidase, xanthine dehydrogenase, nucleoside hydrolases, guanosine deaminase, and hypoxanthine guanine phosphoribosyltransferase, we demonstrate that purine nucleotide catabolism in Arabidopsis (Arabidopsis thaliana) mainly generates xanthosine, but not inosine and hypoxanthine, and that xanthosine is derived from guanosine deamination and a second source, likely xanthosine monophosphate dephosphorylation. Nucleoside hydrolase 1 (NSH1) is known to be essential for xanthosine hydrolysis, but the in vivo function of a second cytosolic nucleoside hydrolase, NSH2, is unclear. We demonstrate that NSH1 activates NSH2 in vitro and in vivo, forming a complex with almost two orders of magnitude higher catalytic efficiency for xanthosine hydrolysis than observed for NSH1 alone. Remarkably, an inactive NSH1 point mutant can activate NSH2 in vivo, fully preventing purine nucleoside accumulation in nsh1 background. Our data lead to an altered model of purine nucleotide catabolism that includes an NSH heterocomplex as a central component.