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AGA
aspartylglucosaminidase
The AGA gene provides instructions for producing aspartylglucosaminidase, an enzyme vital for the breakdown of certain complex sugar-protein molecules within cellular recycling centres called lysosomes. The AGA gene is responsible for encoding the aspartylglucosaminidase enzyme, which plays a critical role in lysosomal degradation pathways.
AGA is located on the long (q) arm of chromosome 4, at band 4q34.3. Arm ratio per GRCh38 - banding schematic.
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Overview
The AGA gene, or aspartylglucosaminidase, encodes an enzyme essential for cellular waste management. This enzyme is primarily active within lysosomes, which are specialised compartments inside cells responsible for breaking down and recycling various molecules. Proper function of the AGA enzyme is crucial for maintaining cellular health and preventing the accumulation of certain complex molecules that can become toxic.
What the gene does
The AGA gene directs the synthesis of the aspartylglucosaminidase enzyme, which functions within lysosomes. Lysosomes act as the cell's recycling centres, where complex molecules are broken down into simpler components. Specifically, this enzyme is involved in degrading glycoproteins, which are proteins with attached sugar chains (oligosaccharides). The aspartylglucosaminidase enzyme cleaves the bond between an asparagine amino acid and an N-acetylglucosamine sugar molecule within these glycoproteins. This cleavage is a critical penultimate step in the complete breakdown of glycoproteins within the lysosome, ensuring that cellular waste products are efficiently processed and removed.
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Chromosome location
The AGA gene is situated on chromosome 4, specifically at position 4q34.3. This genomic location specifies its address within the human genome, where it resides on the long arm (q) of chromosome 4. The gene's precise positioning is essential for its regulated expression and function.
Protein structure
The aspartylglucosaminidase protein consists of 346 amino acids. Domain architecture has not been experimentally characterised in detail for this protein.
Key variants
Variants within the AGA gene can alter the structure and function of the aspartylglucosaminidase enzyme. These genetic changes can affect the enzyme's ability to properly break down glycoproteins, leading to their accumulation within cells. The specific impact of a variant often depends on its location and the resulting change to the protein.
Sample of pathogenic variants
10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.101_107del | p.Trp34fs | Pathogenic | ★★☆☆ | Aspartylglucosaminuria |
c.1018G>T | p.Glu340Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Aspartylglucosaminuria |
c.128-2A>G | - | Pathogenic | ★★☆☆ | Aspartylglucosaminuria |
c.187dup | p.Met63fs | Pathogenic | ★★☆☆ | Aspartylglucosaminuria |
c.192del | p.Cys64fs | Pathogenic/Likely pathogenic | ★★☆☆ | Aspartylglucosaminuria |
c.198_201del | p.Arg66fs | Pathogenic/Likely pathogenic | ★★☆☆ | Aspartylglucosaminuria |
c.1A>G | p.Met1Val | Pathogenic/Likely pathogenic | ★★☆☆ | Aspartylglucosaminuria |
c.200_201del | p.Glu67fs | Pathogenic | ★★☆☆ | Aspartylglucosaminuria |
c.214T>C | p.Ser72Pro | Pathogenic | ★★☆☆ | Aspartylglucosaminuria |
c.302C>T | p.Ala101Val | Pathogenic/Likely pathogenic | ★★☆☆ | Aspartylglucosaminuria |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
Pathogenic variants in the AGA gene are known to cause aspartylglucosaminuria, an inherited metabolic disorder. This condition is characterised by progressive neurological and physical symptoms, primarily affecting mental functioning and movement. The severity and presentation of aspartylglucosaminuria can vary, but it typically worsens over time.
UK clinical status
The AGA gene is included in several expert-curated panels within the UK's NHS Genomic Medicine Service, as listed in PanelApp. It is featured on the DDG2P, Intellectual disability, Likely inborn error of metabolism (R98), Lysosomal storage disorder (R276), Skeletal dysplasia, and Undiagnosed metabolic disorders panels, all of which are rated 'green', indicating strong evidence for gene-disease association and clinical utility.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What is the main function of the AGA gene?
The AGA gene provides instructions for the aspartylglucosaminidase enzyme, which is crucial for breaking down specific glycoprotein molecules within the lysosomes, the cell's recycling centres.
What condition is associated with variants in the AGA gene?
Variants in the AGA gene are associated with aspartylglucosaminuria, a progressive inherited metabolic disorder that primarily affects mental functioning and movement.
Where is the AGA gene located?
The AGA gene is located on chromosome 4, specifically at position 4q34.3 in the human genome.
References
- Saarela J, Oinonen C, Jalanko A. Autoproteolytic activation of human aspartylglucosaminidase. The Biochemical journal. 2004. PMID: 14616088
- Saarela J, Laine M, Oinonen C. Molecular pathogenesis of a disease: structural consequences of aspartylglucosaminuria mutations. Human molecular genetics. 2001. PMID: 11309371
- Aronson NN Jr. Aspartylglycosaminuria: biochemistry and molecular biology. Biochimica et biophysica acta. 1999. PMID: 10571008