The Ureide-Degrading Reactions of Purine Ring Catabolism Employ Three Amidohydrolases and One Aminohydrolase in Arabidopsis, Soybean, and Rice

• Published in: Plant physiology (Bethesda) Vol. 163; no. 2; pp. 672 - 681
• Main Authors: Werner, Andrea K., Medina-Escobar, Nieves, Zulawski, Monika, Sparkes, Imogen A., Cao, Feng-Qiu, Witte, Claus-Peter
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01.10.2013
• Subjects: Amidohydrolases - metabolism; Aminohydrolases - metabolism; Ammonia; Arabidopsis - enzymology; Arabidopsis - growth & development; BIOCHEMISTRY AND METABOLISM; Biological and medical sciences; Catabolism; Enzymes; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant; Gene Silencing; Genetic Complementation Test; Glycine max - enzymology; Glycine max - genetics; Glyoxylates; Kinetics; Leaves; Metabolomics; Models, Biological; Mutation - genetics; Nitrogen; Nitrogen fixation; Nodules; Oryza - enzymology; Plant physiology and development; Plant Proteins - metabolism; Plants; Purines - metabolism; RNA, Messenger - genetics; RNA, Messenger - metabolism; Soybeans; Subcellular Fractions - enzymology; Urea - analogs & derivatives; Urea - metabolism; Monocotyledones; Ureide; Enzyme; Soybean; Glycine max; Arabidopsis thaliana; Grain legume; Oryza; Leguminosae; Plant physiology; Cruciferae; Gramineae; Dicotyledones; Angiospermae; Hydrolases; Herbaceous plant; Spermatophyta; Catabolism; Purine; Experimental plant
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.113.224261

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).