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D312N mutant of human orotidyl-5'-monophosphate decarboxylase in complex with 6-cyano-UMP, covalent adduct
Structural highlights
DiseaseUMPS_HUMAN Defects in UMPS are the cause of orotic aciduria type 1 (ORAC1) [MIM:258900. A disorder of pyrimidine metabolism resulting in megaloblastic anemia and orotic acid crystalluria that is frequently associated with some degree of physical and mental retardation. A minority of cases have additional features, particularly congenital malformations and immune deficiencies.[1] FunctionEvolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedOrotidine-5'-monophosphate decarboxylase (OMPD) catalyzes the decarboxylation of orotidine-5'-monophosphate (OMP) to uridine-5'-monophosphate (UMP) in an extremely proficient manner. The reaction does not require any cofactors and proceeds by an unknown mechanism. In addition to decarboxylation, OMPD is able to catalyze other reactions. We show that several C6-substituted UMP derivatives undergo hydrolysis or substitution reactions that depend on a lysine residue (Lys314) in the OMPD active site. 6-Cyano-UMP is converted to UMP, and UMP derivatives with good leaving groups inhibit OMPD by a suicide mechanism in which Lys314 covalently binds to the substrate. These non-classical reactivities of human OMPD were characterized by cocrystallization and freeze-trapping experiments with wild-type OMPD and two active-site mutants by using substrate and inhibitor nucleotides. The structures show that the C6-substituents are not coplanar with the pyrimidine ring. The extent of this substrate distortion is a function of the substituent geometry. Structure-based mechanisms for the reaction of 6-substituted UMP derivatives are extracted in accordance with results from mutagenesis, mass spectrometry, and OMPD enzyme activity. The Lys314-based mechanisms explain the chemodiversity of OMPD, and offer a strategy to design mechanism-based inhibitors that could be used for antineoplastic purposes for example. Lys314 is a nucleophile in non-classical reactions of orotidine-5'-monophosphate decarboxylase.,Heinrich D, Diederichsen U, Rudolph MG Chemistry. 2009 Jul 6;15(27):6619-25. PMID:19472232[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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