title: Clinical, biochemical and metabolic characterisation of a mild form of human short-chain enoyl-CoA hydratase deficiency: significance of increased N-acetyl-S-(2-carboxypropyl)cysteine excretion.
abstract: BACKGROUND
  Short-chain enoyl-CoA hydratase-ECHS1-catalyses many metabolic pathways, including mitochondrial short-chain fatty acid β-oxidation and branched-chain amino acid catabolic pathways; however, the metabolic products essential for the diagnosis of ECHS1 deficiency have not yet been determined. The objective of this report is to characterise ECHS1 and a mild form of its deficiency biochemically, and to determine the candidate metabolic product that can be efficiently used for neonatal diagnosis.
  
  
  METHODS
  We conducted a detailed clinical, molecular genetics, biochemical and metabolic analysis of sibling patients with ECHS1 deficiency. Moreover, we purified human ECHS1, and determined the substrate specificity of ECHS1 for five substrates via different metabolic pathways.
  
  
  RESULTS
  Human ECHS1 catalyses the hydration of five substrates via different metabolic pathways, with the highest specificity for crotonyl-CoA and the lowest specificity for tiglyl-CoA. The patients had relatively high (∼7%) residual ECHS1 enzyme activity for crotonyl-CoA and methacrylyl-CoA caused by the compound heterozygous mutations (c.176A>G, (p.N59S) and c.413C>T, (p.A138V)) with normal mitochondrial complex I-IV activities. Affected patients excrete large amounts of N-acetyl-S-(2-carboxypropyl)cysteine, a metabolite of methacrylyl-CoA.
  
  
  CONCLUSIONS
  Laboratory data and clinical features demonstrated that the patients have a mild form of ECHS1 deficiency harbouring defective valine catabolic and β-oxidation pathways. N-Acetyl-S-(2-carboxypropyl) cysteine level was markedly high in the urine of the patients, and therefore, N-acetyl-S-(2-carboxypropyl)cysteine was regarded as a candidate metabolite for the diagnosis of ECHS1 deficiency. This metabolite is not part of current routine metabolic screening protocols, and its inclusion, therefore, holds immense potential in accurate diagnosis.
authors.affiliation: Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan.
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Yamada
authors.affiliation: Department of Pediatrics, Toyohashi Municipal Hospital, Toyohashi, Aichi, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Aiba
authors.affiliation: Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Kitaura
authors.affiliation: Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kondo
authors.affiliation: Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Nomura
authors.affiliation: Department of Pediatrics, Toyohashi Municipal Hospital, Toyohashi, Aichi, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nakamura
authors.affiliation: Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Fukushi
authors.affiliation: Department of Metabolism, Chiba Children's Hospital, Chiba, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Murayama
authors.affiliation: Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, Japan.
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Shimomura
authors.affiliation: Victorian Clinical Genetics Services, Murdoch Children's Research Institute, Parkville, Victoria, Australia.
authors.forename: James
authors.initials: J
authors.lastname: Pitt
authors.affiliation: Department of Pediatrics, Faculty of Medicine, Shimane University, Izumo, Shimane, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Yamaguchi
authors.affiliation: Department of Pediatric Neurology, Seirei-Mikatahara General Hospital, Hamamatsu, Shizuoka, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Yokochi
authors.affiliation: Department of Genetics, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan.
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Wakamatsu
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000652:urine; D000214:Acyl Coenzyme A / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D004746:Enoyl-CoA Hydratase / Q000172:deficiency* / Q000378:metabolism; D005260:Female; D006801:Humans; D007564:Japan; D008297:Male; D053858:Metabolic Networks and Pathways; D008661:Metabolism, Inborn Errors / Q000201:enzymology* / Q000503:physiopathology; D009154:Mutation; D014633:Valine / Q000378:metabolism
chemical_list: D000214:Acyl Coenzyme A; C033618:tiglyl-coenzyme A; C054605:N-acetyl-S-(2-carboxypropyl)cysteine; C010701:crotonyl-coenzyme A; D004746:Enoyl-CoA Hydratase; D014633:Valine; D000111:Acetylcysteine
keywords: Genetics; Metabolic disorders; Neurology