title: The biochemistry of nitrogen mobilization: purine ring catabolism.
abstract: The enzymatic route of purine ring catabolism has recently been completed by the discovery of several novel enzymes identified through comparative genome analyses. Here, we review these recent discoveries and present an overview of purine ring catabolism in plants. Xanthine is oxidized to urate in the cytosol, followed by three enzymatic steps taking place in the peroxisome and four reactions in the endoplasmic reticulum releasing the four ring nitrogen as ammonia. Although the main physiological function of purine degradation might lie in the remobilization of nitrogen resources, it has also emerged that catabolic intermediates, the ureides allantoin and allantoate, are likely to be involved in protecting plants against abiotic stress. Conserved alternative splicing mediating the peroxisomal as well as cytosolic localization of allantoin synthase potentially links purine ring catabolism to brassinosteroid signaling.
authors.affiliation: Department of Plant Biochemistry, Dahlem Centre of Plant Sciences, Freie Universität Berlin, Germany.
authors.forename: Andrea K
authors.initials: AK
authors.lastname: Werner
authors.forename: Claus-Peter
authors.initials: CP
authors.lastname: Witte
mesh_terms: D000481:Allantoin / Q000378:metabolism; D002262:Carboxy-Lyases / Q000378:metabolism; D006867:Hydrolases / Q000378:metabolism; D006914:Hydroxysteroids / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism; D010944:Plants / Q000201:enzymology* / Q000378:metabolism; D011687:Purines / Q000378:metabolism*; D015398:Signal Transduction; D014527:Uric Acid / Q000378:metabolism; D019820:Xanthine / Q000378:metabolism
chemical_list: D006914:Hydroxysteroids; D010937:Plant Growth Regulators; D011687:Purines; D019820:Xanthine; D014527:Uric Acid; D000481:Allantoin; D010088:Oxidoreductases; D006867:Hydrolases; D002262:Carboxy-Lyases; D009584:Nitrogen