The Ureide-Degrading Reactions of Purine Ring Catabolism Employ Three Amidohydrolases and One Aminohydrolase in Arabidopsis, Soybean, and Rice1[W]
The Ureide-Degrading Reactions of Purine Ring Catabolism Employ Three Amidohydrolases and One Aminohydrolase in Arabidopsis, Soybean, and Rice1[W]
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DOI：
10.1104/pp.113.224261
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发表时间：
2013-08
期刊：
影响因子：
7.4
通讯作者：
Andrea K. Werner;N. Medina-Escobar;Monika Zulawski;I. Sparkes;Feng-Qiu Cao;C. Witte
中科院分区：
文献类型：
--
作者：
Andrea K. Werner;N. Medina-Escobar;Monika Zulawski;I. Sparkes;Feng-Qiu Cao;C. Witte
氨基水解酶和酰胺水解酶催化植物中嘌呤降解的最后酶促步骤。几种酰脲是嘌呤碱催化剂的中间体，从嘌呤核苷酸释放氮以再同化成氨基酸。在一些豆类如大豆（Glycine max）中，酰脲用于固定氮的根瘤至芽的转运。拟南芥（Arabidopsis thaliana）的四种酶，（1）尿囊素酶，（2）尿囊酸酰胺水解酶（AAH），（3）脲基甘氨酸氨基水解酶，和（4）脲基乙醇酸酰胺水解酶（UAH），在体外催化酰脲尿囊素的完全水解。然而，体内代谢途径仍存在争议。在这里，在拟南芥突变体的生长和代谢产物分析，我们证明，这些酶是必需的尿囊素降解在体内。直链淀粉酶存在于大豆中，由一至四个基因拷贝编码。所有同工酶在体外都有活性，而有些同工酶在体内可能翻译效率低下。令人惊讶的是，转录本和蛋白质的量不显着调节固氮或叶酰脲含量。通过使用病毒诱导的基因沉默已经证明了大豆AAH和UAH对叶片中酰脲催化剂的需求。功能性AAH、脲基甘氨酸氨基水解酶和UAH也存在于水稻（Oryza sativa）中，并且直链脲酸酶基因存在于迄今为止测序的所有其他植物基因组中，表明酰脲降解的酰胺水解酶途径在植物中是通用的，包括苔藓（例如小立碗藓（Physcomitrella patens））和藻类（例如莱茵衣藻（Chlamydomomas reinhardtii））。
Aminohydrolases and amidohydrolases catalyze the last enzymatic steps of purine degradation in plants. Several ureides are intermediates of purine base catabolism, releasing nitrogen from the purine nucleotides for reassimilation into amino acids. In some legumes like soybean (Glycine max), ureides are used for nodule-to-shoot translocation of fixed nitrogen. Four enzymes of Arabidopsis (Arabidopsis thaliana), (1) allantoinase, (2) allantoate amidohydrolase (AAH), (3) ureidoglycine aminohydrolase, and (4) ureidoglycolate amidohydrolase (UAH), catalyze the complete hydrolysis of the ureide allantoin in vitro. However, the metabolic route in vivo remains controversial. Here, in growth and metabolite analyses of Arabidopsis mutants, we demonstrate that these enzymes are required for allantoin degradation in vivo. Orthologous enzymes are present in soybean, encoded by one to four gene copies. All isoenzymes are active in vitro, while some may be inefficiently translated in vivo. Surprisingly, transcript and protein amounts are not significantly regulated by nitrogen fixation or leaf ureide content. A requirement for soybean AAH and UAH for ureide catabolism in leaves has been demonstrated by the use of virus-induced gene silencing. Functional AAH, ureidoglycine aminohydrolase, and UAH are also present in rice (Oryza sativa), and orthologous genes occur in all other plant genomes sequenced to date, indicating that the amidohydrolase route of ureide degradation is universal in plants, including mosses (e.g. Physcomitrella patens) and algae (e.g. Chlamydomomas reinhardtii).