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

ALDH gene family

Reviewed October 2011

What are the ALDH genes?

Genes in the aldehyde dehydrogenase (ALDH) gene family provide instructions for making enzymes that are involved in the breakdown (metabolism) of various molecules within cells. Aldehyde dehydrogenase enzymes play a role in the metabolism of many molecules including certain fats (cholesterol and other fatty acids) and protein building blocks (amino acids). Additional aldehyde dehydrogenase enzymes detoxify substances, such as alcohol, pollutants, and toxins that are formed within cells. The specific role of aldehyde dehydrogenase enzymes is to alter groups of oxygen, carbon, and hydrogen atoms (collectively called an aldehyde group) that are attached to other molecules. Aldehyde groups can be beneficial or damaging to cells and tissues, depending on the molecule to which they are attached. Through their action in altering aldehyde groups, aldehyde dehydrogenase enzymes produce molecules called NADPH and NADH, which are necessary for many cellular processes.

Aldehyde dehydrogenase enzymes are primarily found in liver and kidney cells but are also located in other cells throughout the body. Within cells, aldehyde dehydrogenase enzymes are located in a structure involved in protein processing and transport (endoplasmic reticulum), the energy-producing centers of cells (mitochondria), the internal fluid of the cell (cytosol), and the nucleus. Aldehyde dehydrogenase enzymes interact with many different kinds of molecules depending on the enzymes' location within the cell.

Common variations (polymorphisms) in ALDH genes can affect the function of the enzymes that are produced. Polymorphisms in the ALDH2 gene, for example, affect the breakdown of alcohol. People who have a certain polymorphism in the ALDH2 gene that disrupts the functioning of the enzyme have a decreased tolerance for alcohol.

Diseases caused by mutations in ALDH genes typically involve the buildup of substances in the body that are harmful in large amounts or that impair the function or production of other necessary molecules.

The name of each aldehyde dehydrogenase gene begins with ALDH, indicating that it is part of the aldehyde dehydrogenase gene family. The gene is also given a number associated with a specific group within the gene family, a letter representing the gene's subfamily, and a number assigned to the specific gene within the subfamily. For example, the first aldehyde dehydrogenase gene in group 7, subfamily A, is written as ALDH7A1. Researchers have identified 19 ALDH genes in humans.

Which genes are included in the ALDH gene family?

The HUGO Gene Nomenclature Committee (HGNC) provides an index of gene families ( and their member genes.

Genetics Home Reference summarizes the normal function and health implications of these members of the ALDH gene family: ALDH3A2, ALDH4A1, ALDH5A1, and ALDH7A1.

What conditions are related to genes in the ALDH gene family?

Genetics Home Reference includes these conditions related to genes in the ALDH gene family:

  • hyperprolinemia
  • pyridoxine-dependent epilepsy
  • Sjögren-Larsson syndrome
  • succinic semialdehyde dehydrogenase deficiency

What glossary definitions help with understanding the ALDH gene family?

acids ; aldehyde ; breakdown ; cell ; cholesterol ; cytosol ; dehydrogenase ; endoplasmic reticulum ; enzyme ; fatty acids ; gene ; kidney ; metabolism ; mitochondria ; molecule ; nucleus ; oxygen ; polymorphism ; protein

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


These sources were used to develop the Genetics Home Reference summary for the ALDH gene family.

  • Sládek NE. Human aldehyde dehydrogenases: potential pathological, pharmacological, and toxicological impact. J Biochem Mol Toxicol. 2003;17(1):7-23. Review. (
  • Vasiliou V, Pappa A, Petersen DR. Role of aldehyde dehydrogenases in endogenous and xenobiotic metabolism. Chem Biol Interact. 2000 Dec 1;129(1-2):1-19. Review. (
  • Vasiliou V, Nebert DW. Analysis and update of the human aldehyde dehydrogenase (ALDH) gene family. Hum Genomics. 2005 Jun;2(2):138-43. (
  • Sophos NA, Vasiliou V. Aldehyde dehydrogenase gene superfamily: the 2002 update. Chem Biol Interact. 2003 Feb 1;143-144:5-22. (
  • Marchitti SA, Deitrich RA, Vasiliou V. Neurotoxicity and metabolism of the catecholamine-derived 3,4-dihydroxyphenylacetaldehyde and 3,4-dihydroxyphenylglycolaldehyde: the role of aldehyde dehydrogenase. Pharmacol Rev. 2007 Jun;59(2):125-50. Epub 2007 Mar 22. Review. (
  • Vasiliou V, Pappa A. Polymorphisms of human aldehyde dehydrogenases. Consequences for drug metabolism and disease. Pharmacology. 2000 Sep;61(3):192-8. 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: October 2011
Published: February 1, 2016