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


Reviewed August 2009

What is the official name of the AASS gene?

The official name of this gene is “aminoadipate-semialdehyde synthase.”

AASS is the gene's official symbol. The AASS gene is also known by other names, listed below.

What is the normal function of the AASS gene?

The AASS gene provides instructions for making an enzyme called aminoadipic semialdehyde synthase. This enzyme is found in most tissues, with the highest amounts found in the liver. Aminoadipic semialdehyde synthase is involved in the breakdown of the amino acid lysine, a building block of most proteins. It is called a bifunctional enzyme because is performs two functions. One function, called lysine-ketoglutarate reductase, breaks down lysine to a molecule called saccharopine. The other function, called saccharopine dehydrogenase, breaks down saccharopine to a molecule called alpha-aminoadipate semialdehyde.

How are changes in the AASS gene related to health conditions?

hyperlysinemia - caused by mutations in the AASS gene

At least five mutations in the AASS gene have been found to cause hyperlysinemia. Most of these mutations change single amino acids in aminoadipic semialdehyde synthase. These mutations are thought to decrease or eliminate enzyme activity, resulting in an inability to break down lysine. Lysine that is not broken down accumulates in the blood, but it typically causes no health problems.

When mutations in the AASS gene impair the breakdown of saccharopine, this molecule builds up in blood and urine. This buildup is sometimes referred to as saccharopinuria, which is considered to be a variant of hyperlysinemia. It is unclear if saccharopinuria causes any symptoms.

Where is the AASS gene located?

Cytogenetic Location: 7q31.3

Molecular Location on chromosome 7: base pairs 122,073,544 to 122,144,290

(Homo sapiens Annotation Release 107, GRCh38.p2) (NCBI (

The AASS gene is located on the long (q) arm of chromosome 7 at position 31.3.

The AASS gene is located on the long (q) arm of chromosome 7 at position 31.3.

More precisely, the AASS gene is located from base pair 122,073,544 to base pair 122,144,290 on chromosome 7.

See How do geneticists indicate the location of a gene? ( in the Handbook.

Where can I find additional information about AASS?

You and your healthcare professional may find the following resources about AASS helpful.

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

What other names do people use for the AASS gene or gene products?

  • alpha-aminoadipate semialdehyde synthase
  • aminoadipic semialdehyde synthase
  • lysine-2-oxoglutarate reductase
  • lysine-ketoglutarate reductase /saccharopine dehydrogenase

See How are genetic conditions and genes named? ( in the Handbook.

What glossary definitions help with understanding AASS?

acids ; amino acid ; breakdown ; dehydrogenase ; enzyme ; gene ; lysine ; molecule

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


  • Markovitz PJ, Chuang DT, Cox RP. Familial hyperlysinemias. Purification and characterization of the bifunctional aminoadipic semialdehyde synthase with lysine-ketoglutarate reductase and saccharopine dehydrogenase activities. J Biol Chem. 1984 Oct 10;259(19):11643-6. (
  • NCBI Gene (
  • Sacksteder KA, Biery BJ, Morrell JC, Goodman BK, Geisbrecht BV, Cox RP, Gould SJ, Geraghty MT. Identification of the alpha-aminoadipic semialdehyde synthase gene, which is defective in familial hyperlysinemia. Am J Hum Genet. 2000 Jun;66(6):1736-43. Epub 2000 Apr 20. (
  • Saudubray JM, Rabier D. Biomarkers identified in inborn errors for lysine, arginine, and ornithine. J Nutr. 2007 Jun;137(6 Suppl 2):1669S-1672S. Review. (


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: August 2009
Published: February 8, 2016