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Reviewed July 2009

What is the official name of the ALAS2 gene?

The official name of this gene is “5'-aminolevulinate synthase 2.”

ALAS2 is the gene's official symbol. The ALAS2 gene is also known by other names, listed below.

Read more about gene names and symbols on the About page.

What is the normal function of the ALAS2 gene?

The ALAS2 gene provides instructions for making an enzyme called 5'-aminolevulinate synthase 2 or erythroid ALA-synthase. This version of the enzyme is found only in developing red blood cells called erythroblasts.

ALA-synthase plays an important role in the production of heme. Heme is a component of iron-containing proteins called hemoproteins, including hemoglobin (the protein that carries oxygen in the blood). Heme is vital for all of the body's organs, although it is most abundant in the blood, bone marrow, and liver.

The production of heme is a multi-step process that requires eight different enzymes. ALA-synthase is responsible for the first step in this process, the formation of a compound called delta-aminolevulinic acid (ALA). In subsequent steps, seven other enzymes produce and modify compounds that ultimately lead to heme.

How are changes in the ALAS2 gene related to health conditions?

porphyria - caused by mutations in the ALAS2 gene

At least two ALAS2 gene mutations have been found in people with a form of porphyria known as X-linked dominant erythropoietic protoporphyria. Each of these mutations deletes a small amount of genetic material near the end of the ALAS2 gene. These changes overactivate erythroid ALA-synthase, which increases the production of ALA within red blood cells. The excess ALA is converted by other enzymes to compounds called porphyrins. If these compounds build up in erythroblasts, they can leak out and be transported through the bloodstream to the skin and other tissues. High levels of porphyrins in the skin cause the oversensitivity to sunlight that is characteristic of this condition.

X-linked sideroblastic anemia - caused by mutations in the ALAS2 gene

At least 50 mutations that cause X-linked sideroblastic anemia have been identified in the ALAS2 gene. Almost all of these mutations change single protein building blocks (amino acids) in erythroid ALA-synthase. These changes impair the activity of the enzyme, which disrupts the normal production of heme in developing red blood cells. A reduction in the amount of heme prevents these cells from making enough hemoglobin. Because almost all of the iron transported into erythroblasts is normally incorporated into heme, the reduced production of heme leads to a buildup of excess iron in these cells. Additionally, the body attempts to compensate for the hemoglobin shortage by absorbing more iron from the diet. This buildup of excess iron can damage the body's organs. Low hemoglobin levels and the resulting accumulation of iron in the body's organs lead to the characteristic features of X-linked sideroblastic anemia.

Where is the ALAS2 gene located?

Cytogenetic Location: Xp11.21

Molecular Location on the X chromosome: base pairs 55,009,055 to 55,031,064

(Homo sapiens Annotation Release 107, GRCh38.p2) (NCBIThis link leads to a site outside Genetics Home Reference.)

The ALAS2 gene is located on the short (p) arm of the X chromosome at position 11.21.

The ALAS2 gene is located on the short (p) arm of the X chromosome at position 11.21.

More precisely, the ALAS2 gene is located from base pair 55,009,055 to base pair 55,031,064 on the X chromosome.

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

Where can I find additional information about ALAS2?

You and your healthcare professional may find the following resources about ALAS2 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 ALAS2 gene or gene products?

  • 5-aminolevulinate synthase, erythroid-specific, mitochondrial
  • ALAS-E
  • ALAS, erythroid
  • aminolevulinate, delta-, synthase 2
  • ANH1
  • ASB

Where can I find general information about genes?

The Handbook provides basic information about genetics in clear language.

These links provide additional genetics resources that may be useful.

What glossary definitions help with understanding ALAS2?

acids ; Ala ; anemia ; bone marrow ; compound ; enzyme ; erythrocyte ; gene ; heme ; hemoglobin ; iron ; oxygen ; protein ; X-linked dominant

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

See also Understanding Medical Terminology.

References (13 links)


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: July 2009
Published: February 8, 2016