Agradecimentos: Declaration of competing interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. This work received financial support from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, #402440/2021-8), Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS, #19/2551-0001662-0), Pró-Reitoria de Pesquisa/Universidade Federal do Rio Grande do Sul (PROPESq/UFRGS, #42875), Instituto Nacional de Ciência e Tecnologia–Excitotoxicidade e Neuroproteção (INCT-EN, #465671/2014–4), Instituto Nacional de Ciência e Tecnologia–Saúde Cerebral (INCT-SC; #406020/2022-1), and Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP; #17/17728-8). Research of JOS is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Projektnummer 514177501 Ver menos

Abstract: Aminoacylase 1 (ACY1) deficiency is an inherited metabolic disorder biochemically characterized by high urinary concentrations of aliphatic N-acetylated amino acids and associated with a broad clinical spectrum with predominant neurological signs. Considering that the pathogenesis of ACY1 is practically unknown and the brain is highly dependent on energy production, the in vitro effects of N-acetylglutamate (NAG) and N-acetylmethionine (NAM), major metabolites accumulating in ACY1 deficiency, on the enzyme activities of the citric acid cycle (CAC), of the respiratory chain complexes and glutamate dehydrogenase (GDH), as well as on ATP synthesis were evaluated in brain mitochondrial preparations of developing rats. NAG mildly inhibited mitochondrial isocitrate dehydrogenase 2 (IDH2) activity, moderately inhibited the activities of isocitrate dehydrogenase 3 (IDH3) and complex II-III of the respiratory chain and markedly suppressed the activities of complex IV and GDH. Of note, the NAG-induced inhibitory effect on IDH3 was competitive, whereas that on GDH was mixed. On the other hand, NAM moderately inhibited the activity of respiratory complexes II-III and GDH activities and strongly decreased complex IV activity. Furthermore, NAM was unable to modify any of the CAC enzyme activities, indicating a selective effect of NAG toward IDH mitochondrial isoforms. In contrast, the activities of citrate synthase, a-ketoglutarate dehydrogenase, malate dehydrogenase, and of the respiratory chain complexes I and II were not changed by these N-acetylated amino acids. Finally, NAG and NAM strongly decreased mitochondrial ATP synthesis. Taken together, the data indicate that NAG and NAM impair mitochondrial brain energy homeostasis Ver menos