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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®

Aminoacylase 1 deficiency

Reviewed May 2014

What is aminoacylase 1 deficiency?

Aminoacylase 1 deficiency is an inherited disorder that can cause neurological problems; the pattern and severity of signs and symptoms vary widely among affected individuals. Individuals with this condition typically have delayed development of mental and motor skills (psychomotor delay). They can have movement problems, reduced muscle tone (hypotonia), mild intellectual disability, and seizures. However, some people with aminoacylase 1 deficiency have no health problems related to the condition. A key feature common to all people with aminoacylase 1 deficiency is high levels of modified protein building blocks (amino acids), called N-acetylated amino acids, in the urine.

How common is aminoacylase 1 deficiency?

The prevalence of aminoacylase 1 deficiency is unknown.

What genes are related to aminoacylase 1 deficiency?

Aminoacylase 1 deficiency is caused by mutations in the ACY1 gene. This gene provides instructions for making an enzyme called aminoacylase 1, which is involved in the breakdown of proteins when they are no longer needed. Many proteins in the body have an acetyl group attached to one end. This modification, called N-acetylation, helps protect and stabilize the protein. Aminoacylase 1 performs the final step in the breakdown of these proteins by removing the acetyl group from certain amino acids. The amino acids can then be recycled and used to build other proteins.

Mutations in the ACY1 gene lead to an aminoacylase 1 enzyme with little or no function. Without this enzyme's function, acetyl groups are not efficiently removed from a subset of amino acids during the breakdown of proteins. The excess N-acetylated amino acids are released from the body in urine. It is not known how a reduction of aminoacylase 1 function leads to neurological problems in people with aminoacylase 1 deficiency.

Related Gene(s)

Changes in this gene are associated with aminoacylase 1 deficiency.

  • ACY1

How do people inherit aminoacylase 1 deficiency?

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Where can I find information about diagnosis or management of aminoacylase 1 deficiency?

These resources address the diagnosis or management of aminoacylase 1 deficiency and may include treatment providers.

  • Genetic Testing Registry: Aminoacylase 1 deficiency (

You might also find information on the diagnosis or management of aminoacylase 1 deficiency in Educational resources and Patient support.

General information about the diagnosis ( and management ( of genetic conditions is available in the Handbook. Read more about genetic testing (, particularly the difference between clinical tests and research tests (

To locate a healthcare provider, see How can I find a genetics professional in my area? ( in the Handbook.

Where can I find additional information about aminoacylase 1 deficiency?

You may find the following resources about aminoacylase 1 deficiency helpful. These materials are written for the general public.

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

What other names do people use for aminoacylase 1 deficiency?

  • ACY1D
  • deficiency of the aminoacylase-1 enzyme

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines ( and How are genetic conditions and genes named? ( in the Handbook.

What if I still have specific questions about aminoacylase 1 deficiency?

Ask the Genetic and Rare Diseases Information Center (

What glossary definitions help with understanding aminoacylase 1 deficiency?

acids ; autosomal ; autosomal recessive ; breakdown ; cell ; deficiency ; disability ; enzyme ; gene ; hypotonia ; inherited ; motor ; muscle tone ; neurological ; prevalence ; protein ; psychomotor ; recessive

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • Engelke UF, Sass JO, Van Coster RN, Gerlo E, Olbrich H, Krywawych S, Calvin J, Hart C, Omran H, Wevers RA. NMR spectroscopy of aminoacylase 1 deficiency, a novel inborn error of metabolism. NMR Biomed. 2008 Feb;21(2):138-47. (
  • Ferri L, Funghini S, Fioravanti A, Biondi EG, la Marca G, Guerrini R, Donati MA, Morrone A. Aminoacylase I deficiency due to ACY1 mRNA exon skipping. Clin Genet. 2014 Oct;86(4):367-72. doi: 10.1111/cge.12297. Epub 2013 Nov 18. (
  • Sass JO, Mohr V, Olbrich H, Engelke U, Horvath J, Fliegauf M, Loges NT, Schweitzer-Krantz S, Moebus R, Weiler P, Kispert A, Superti-Furga A, Wevers RA, Omran H. Mutations in ACY1, the gene encoding aminoacylase 1, cause a novel inborn error of metabolism. Am J Hum Genet. 2006 Mar;78(3):401-9. Epub 2006 Jan 18. (
  • Sass JO, Olbrich H, Mohr V, Hart C, Woldseth B, Krywawych S, Bjurulf B, Lakhani PK, Buchdahl RM, Omran H. Neurological findings in aminoacylase 1 deficiency. Neurology. 2007 Jun 12;68(24):2151-3. (
  • Sommer A, Christensen E, Schwenger S, Seul R, Haas D, Olbrich H, Omran H, Sass JO. The molecular basis of aminoacylase 1 deficiency. Biochim Biophys Acta. 2011 Jun;1812(6):685-90. doi: 10.1016/j.bbadis.2011.03.005. Epub 2011 Mar 23. (
  • Tylki-Szymanska A, Gradowska W, Sommer A, Heer A, Walter M, Reinhard C, Omran H, Sass JO, Jurecka A. Aminoacylase 1 deficiency associated with autistic behavior. J Inherit Metab Dis. 2010 Dec;33 Suppl 3:S211-4. doi: 10.1007/s10545-010-9089-3. Epub 2010 May 18. (


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? ( in the Handbook.

Reviewed: May 2014
Published: February 1, 2016