title: Structural and functional insights into (S)-ureidoglycine aminohydrolase, key enzyme of purine catabolism in Arabidopsis thaliana.
abstract: The ureide pathway has recently been identified as the metabolic route of purine catabolism in plants and some bacteria. In this pathway, uric acid, which is a major product of the early stage of purine catabolism, is degraded into glyoxylate and ammonia via stepwise reactions of seven different enzymes. Therefore, the pathway has a possible physiological role in mobilization of purine ring nitrogen for further assimilation. (S)-Ureidoglycine aminohydrolase enzyme converts (S)-ureidoglycine into (S)-ureidoglycolate and ammonia, providing the final substrate to the pathway. Here, we report a structural and functional analysis of this enzyme from Arabidopsis thaliana (AtUGlyAH). The crystal structure of AtUGlyAH in the ligand-free form shows a monomer structure in the bicupin fold of the β-barrel and an octameric functional unit as well as a Mn(2+) ion binding site. The structure of AtUGlyAH in complex with (S)-ureidoglycine revealed that the Mn(2+) ion acts as a molecular anchor to bind (S)-ureidoglycine, and its binding mode dictates the enantioselectivity of the reaction. Further kinetic analysis characterized the functional roles of the active site residues, including the Mn(2+) ion binding site and residues in the vicinity of (S)-ureidoglycine. These analyses provide molecular insights into the structure of the enzyme and its possible catalytic mechanism.
authors.affiliation: Department of Agricultural Biotechnology, Seoul National University, Seoul, Korea.
authors.forename: Inchul
authors.initials: I
authors.lastname: Shin
authors.forename: Riccardo
authors.initials: R
authors.lastname: Percudani
authors.forename: Sangkee
authors.initials: S
authors.lastname: Rhee
mesh_terms: D000595:Amino Acid Sequence; D000619:Aminohydrolases / Q000737:chemistry / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011687:Purines / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D029681:Arabidopsis Proteins; D011687:Purines; D000619:Aminohydrolases; C546345:ureidoglycine aminohydrolase, Arabidopsis