title: Mutations in ACY1, the gene encoding aminoacylase 1, cause a novel inborn error of metabolism.
abstract: N-terminal acetylation of proteins is a widespread and highly conserved process. Aminoacylase 1 (ACY1; EC 3.5.14) is the most abundant of the aminoacylases, a class of enzymes involved in hydrolysis of N-acetylated proteins. Here, we present four children with genetic deficiency of ACY1. They were identified through organic acid analyses using gas chromatography-mass spectrometry, revealing increased urinary excretion of several N-acetylated amino acids, including the derivatives of methionine, glutamic acid, alanine, leucine, glycine, valine, and isoleucine. Nuclear magnetic resonance spectroscopy analysis of urine samples detected a distinct pattern of N-acetylated metabolites, consistent with ACY1 dysfunction. Functional analyses of patients' lymphoblasts demonstrated ACY1 deficiency. Mutation analysis uncovered recessive loss-of-function or missense ACY1 mutations in all four individuals affected. We conclude that ACY1 mutations in these children led to functional ACY1 deficiency and excretion of N-acetylated amino acids. Questions remain, however, as to the clinical significance of ACY1 deficiency. The ACY1-deficient individuals were ascertained through urine metabolic screening because of unspecific psychomotor delay (one subject), psychomotor delay with atrophy of the vermis and syringomyelia (one subject), marked muscular hypotonia (one subject), and follow-up for early treated biotinidase deficiency and normal clinical findings (one subject). Because ACY1 is evolutionarily conserved in fish, frog, mouse, and human and is expressed in the central nervous system (CNS) in human, a role in CNS function or development is conceivable but has yet to be demonstrated. Thus, at this point, we cannot state whether ACY1 deficiency has pathogenic significance with pleiotropic clinical expression or is simply a biochemical variant. Awareness of this new genetic entity may help both in delineating its clinical significance and in avoiding erroneous diagnoses.
authors.affiliation: Department of General Pediatrics and Adolescent Medicine, University Children's Hospital Freiburg, Freiburg, Germany. Sass@kikLi.ukL.uni-freiburg.de
authors.forename: Jorn Oliver
authors.initials: JO
authors.lastname: Sass
authors.forename: Verena
authors.initials: V
authors.lastname: Mohr
authors.forename: Heike
authors.initials: H
authors.lastname: Olbrich
authors.forename: Udo
authors.initials: U
authors.lastname: Engelke
authors.forename: Judit
authors.initials: J
authors.lastname: Horvath
authors.forename: Manfred
authors.initials: M
authors.lastname: Fliegauf
authors.forename: Niki Tomas
authors.initials: NT
authors.lastname: Loges
authors.forename: Susanne
authors.initials: S
authors.lastname: Schweitzer-Krantz
authors.forename: Ralf
authors.initials: R
authors.lastname: Moebus
authors.forename: Polly
authors.initials: P
authors.lastname: Weiler
authors.forename: Andreas
authors.initials: A
authors.lastname: Kispert
authors.forename: Andrea
authors.initials: A
authors.lastname: Superti-Furga
authors.forename: Ron A
authors.initials: RA
authors.lastname: Wevers
authors.forename: Heymut
authors.initials: H
authors.lastname: Omran
mesh_terms: D000107:Acetylation; D000581:Amidohydrolases / Q000172:deficiency / Q000235:genetics*; D000592:Amino Acid Metabolism, Inborn Errors / Q000235:genetics*; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism* / Q000652:urine; D000818:Animals; D015152:Blotting, Northern; D002648:Child; D017124:Conserved Sequence; D005796:Genes; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D051381:Rats; D016415:Sequence Alignment
chemical_list: D000596:Amino Acids; D000581:Amidohydrolases; C019672:aminoacylase I