Skip navigation

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

URL of this page:

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.


The prevalence of aminoacylase 1 deficiency is unknown.


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.


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.

Other Names for This Condition

  • ACY1D
  • Deficiency of the aminoacylase-1 enzyme

Additional Information & Resources

Genetic and Rare Diseases Information Center

Patient Support and Advocacy Resources

Catalog of Genes and Diseases from OMIM

Scientific Articles on PubMed


  • 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. doi: 10.1002/nbm.1170. Citation on PubMed
  • 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. Citation on PubMed
  • 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. doi: 10.1086/500563. Epub 2006 Jan 18. Citation on PubMed or Free article on PubMed Central
  • 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. doi: 10.1212/01.wnl.0000264933.56204.e8. No abstract available. Citation on PubMed
  • 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. Citation on PubMed
  • 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. Citation on PubMed

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.