TY - JOUR
T1 - Inhibition of N-acetylglutamate synthase by various monocarboxylic and dicarboxylic short-chain coenzyme A esters and the production of alternative glutamate esters
AU - Dercksen, M.
AU - IJlst, L.
AU - Duran, M.
AU - Mienie, L. J.
AU - van Cruchten, A.
AU - van der Westhuizen, F. H.
AU - Wanders, R. J. A.
PY - 2014
Y1 - 2014
N2 - 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
AB - 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
U2 - https://doi.org/10.1016/j.bbadis.2013.04.027
DO - https://doi.org/10.1016/j.bbadis.2013.04.027
M3 - Article
C2 - 23643712
SN - 0925-4439
VL - 1842
SP - 2510
EP - 2516
JO - Biochimica et Biophysica Acta-Molecular Basis of Disease
JF - Biochimica et Biophysica Acta-Molecular Basis of Disease
IS - 12 Part A
ER -