title: Inhibition of N-acetylglutamate synthase by various monocarboxylic and dicarboxylic short-chain coenzyme A esters and the production of alternative glutamate esters.
abstract: Hyperammonemia is a frequent finding in various organic acidemias. One possible mechanism involves the inhibition of the enzyme N-acetylglutamate synthase (NAGS), by short-chain acyl-CoAs which accumulate due to defective catabolism of amino acids and/or fatty acids in the cell. The aim of this study was to investigate the effect of various acyl-CoAs on the activity of NAGS in conjunction with the formation of glutamate esters. NAGS activity was measured in vitro using a sensitive enzyme assay with ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) product analysis. Propionyl-CoA and butyryl-CoA proved to be the most powerful inhibitors of N-acetylglutamate (NAG) formation. Branched-chain amino acid related CoAs (isovaleryl-CoA, 3-methylcrotonyl-CoA, isobutyryl-CoA) showed less pronounced inhibition of NAGS whereas the dicarboxylic short-chain acyl-CoAs (methylmalonyl-CoA, succinyl-CoA, glutaryl-CoA) had the least inhibitory effect. Subsequent work showed that the most powerful inhibitors also proved to be the best substrates in the formation of N-acylglutamates. Furthermore, we identified N-isovalerylglutamate, N-3-methylcrotonylglutamate and N-isobutyrylglutamate (the latter two in trace amounts), in the urines of patients with different organic acidemias. Collectively, these findings explain one of the contributing factors to secondary hyperammonemia, which lead to the reduced in vivo flux through the urea cycle in organic acidemias and result in the inadequate elimination of ammonia.
authors: Laboratory Genetic Metabolic Diseases, Departments of Pediatrics and Clinical Chemistry, Academic Medical Centre, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; Centre for Human Metabonomics, North-West University (Potchefstroom Campus), Hoffman street 11, Potchefstroom, South Africa, 2520. Electronic address: marli.dercksen@nwu.ac.za.
authors: M
authors: M
authors: Dercksen
authors: Laboratory Genetic Metabolic Diseases, Departments of Pediatrics and Clinical Chemistry, Academic Medical Centre, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.
authors: L
authors: L
authors: IJlst
authors: Laboratory Genetic Metabolic Diseases, Departments of Pediatrics and Clinical Chemistry, Academic Medical Centre, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.
authors: M
authors: M
authors: Duran
authors: Centre for Human Metabonomics, North-West University (Potchefstroom Campus), Hoffman street 11, Potchefstroom, South Africa, 2520.
authors: L J
authors: LJ
authors: Mienie
authors: Laboratory Genetic Metabolic Diseases, Departments of Pediatrics and Clinical Chemistry, Academic Medical Centre, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.
authors: A
authors: A
authors: van Cruchten
authors: Centre for Human Metabonomics, North-West University (Potchefstroom Campus), Hoffman street 11, Potchefstroom, South Africa, 2520.
authors: F H
authors: FH
authors: van der Westhuizen
authors: Laboratory Genetic Metabolic Diseases, Departments of Pediatrics and Clinical Chemistry, Academic Medical Centre, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.
authors: R J A
authors: RJ
authors: Wanders
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism / Q000494:pharmacology*; D051046:Amino-Acid N-Acetyltransferase / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D002264:Carboxylic Acids / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003998:Dicarboxylic Acids / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004952:Esters; D018698:Glutamic Acid / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D022124:Hyperammonemia / Q000378:metabolism; D007700:Kinetics; D053719:Tandem Mass Spectrometry
chemical_list: D000214:Acyl Coenzyme A; D002264:Carboxylic Acids; D003998:Dicarboxylic Acids; D004952:Esters; C015357:methylmalonyl-coenzyme A; C050106:isobutyryl-coenzyme A; C024343:butyryl-coenzyme A; C015901:glutaryl-coenzyme A; C009061:propionyl-coenzyme A; D018698:Glutamic Acid; C017447:isovaleryl-coenzyme A; C012046:succinyl-coenzyme A; D051046:Amino-Acid N-Acetyltransferase
keywords: Acyl-CoAs; Branched-chain amino acids; Hyperammonemia; N-acetylglutamate synthase; N-acylglutamates; Organic acidemia