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AGA gene


Normal Function

The AGA gene provides instructions for producing an enzyme called aspartylglucosaminidase. This enzyme is active in lysosomes, which are structures inside cells that act as recycling centers. Within lysosomes, the enzyme helps break down complex chains of sugar molecules (oligosaccharides) attached to certain proteins (glycoproteins). Specifically, this enzyme cuts (cleaves) glycoproteins between a protein building block (amino acid) called asparagine and a sugar molecule called N-acetylglucosamine. This cut is one of the last steps in breaking down a glycoprotein in the lysosome.

Health Conditions Related to Genetic Changes


Many variants (also known as mutations) in the AGA gene have been found to cause aspartylglucosaminuria. This condition primarily affects mental functioning and movement. Aspartylglucosaminuria worsens over time. Most AGA gene variants change one amino acid in aspartylglucosaminidase. One variant, found in 98 percent of people with this condition in Finland, replaces the amino acid cysteine with the amino acid serine at position 163 in the enzyme (written as Cys163Ser or C163S). 

Many AGA gene variants, including C163S, disrupt the structure of aspartylglucosaminidase, resulting in an enzyme that cannot effectively break down glycoproteins because it cannot make the cut between asparagine and N-acetylglucosamine. A buildup of glycoproteins seems to particularly affect nerve cells in the brain; loss of these cells causes a progressive decline in mental functioning and the other signs and symptoms of aspartylglucosaminuria.

More About This Health Condition

Other Names for This Gene

  • ASRG
  • glycosylasparaginase
  • N(4)-(beta-N-acetylglucosaminyl)-L-asparaginase
  • N4-(N-acetyl-beta-glucosaminyl)-L-asparagine amidase

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases


  • Aronson NN Jr. Aspartylglycosaminuria: biochemistry and molecular biology. Biochim Biophys Acta. 1999 Oct 8;1455(2-3):139-54. doi: 10.1016/s0925-4439(99)00076-9. Citation on PubMed
  • Arvio M, Mononen I. Aspartylglycosaminuria: a review. Orphanet J Rare Dis. 2016 Dec 1;11(1):162. doi: 10.1186/s13023-016-0544-6. Citation on PubMed
  • Goodspeed K, Feng C, Laine M, Lund TC. Aspartylglucosaminuria: Clinical Presentation and Potential Therapies. J Child Neurol. 2021 Apr;36(5):403-414. doi: 10.1177/0883073820980904. Epub 2021 Jan 13. Citation on PubMed
  • Saarela J, Laine M, Oinonen C, von Schantz C, Jalanko A, Rouvinen J, Peltonen L. Molecular pathogenesis of a disease: structural consequences of aspartylglucosaminuria mutations. Hum Mol Genet. 2001 Apr 15;10(9):983-95. doi: 10.1093/hmg/10.9.983. Citation on PubMed
  • Saarela J, Oinonen C, Jalanko A, Rouvinen J, Peltonen L. Autoproteolytic activation of human aspartylglucosaminidase. Biochem J. 2004 Mar 1;378(Pt 2):363-71. doi: 10.1042/BJ20031496. Citation on PubMed or Free article on PubMed Central

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.