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


Reviewed July 2009

What is the official name of the ALAS1 gene?

The official name of this gene is “5'-aminolevulinate synthase 1.”

ALAS1 is the gene's official symbol. The ALAS1 gene is also known by other names, listed below.

What is the normal function of the ALAS1 gene?

The ALAS1 gene provides instructions for making an enzyme called 5'-aminolevulinate synthase 1 or ALA-synthase. ALAS1 is one of two genes that carry instructions for making versions of the ALA-synthase enzyme. The other ALA-synthase gene, ALAS2, is turned on (active) only in developing red blood cells (erythroblasts). The ALAS1 gene is active in cells throughout the body.

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.

Where is the ALAS1 gene located?

Cytogenetic Location: 3p21.1

Molecular Location on chromosome 3: base pairs 52,198,082 to 52,214,326

The ALAS1 gene is located on the short (p) arm of chromosome 3 at position 21.1.

The ALAS1 gene is located on the short (p) arm of chromosome 3 at position 21.1.

More precisely, the ALAS1 gene is located from base pair 52,198,082 to base pair 52,214,326 on chromosome 3.

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

Where can I find additional information about ALAS1?

You and your healthcare professional may find the following resources about ALAS1 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 ALAS1 gene or gene products?

  • 5-aminolevulinate synthase
  • 5-aminolevulinate synthase, nonspecific, mitochondrial
  • 5-aminolevulinic acid synthase
  • ALAS3
  • ALAS-H
  • ALAS, housekeeping type
  • ALA-synthase
  • aminolevulinate, delta-, synthase 1
  • Delta-ALA synthetase
  • Delta-aminolevulinate synthase

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

What glossary definitions help with understanding ALAS1?

Ala ; bone marrow ; compound ; enzyme ; gene ; heme ; hemoglobin ; iron ; oxygen ; protein

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


  • Cotter PD, Drabkin HA, Varkony T, Smith DI, Bishop DF. Assignment of the human housekeeping delta-aminolevulinate synthase gene (ALAS1) to chromosome band 3p21.1 by PCR analysis of somatic cell hybrids. Cytogenet Cell Genet. 1995;69(3-4):207-8. (
  • Kauppinen R. Porphyrias. Lancet. 2005 Jan 15-21;365(9455):241-52. Review. (
  • NCBI Gene (
  • Podvinec M, Handschin C, Looser R, Meyer UA. Identification of the xenosensors regulating human 5-aminolevulinate synthase. Proc Natl Acad Sci U S A. 2004 Jun 15;101(24):9127-32. Epub 2004 Jun 3. (
  • Roberts AG, Elder GH. Alternative splicing and tissue-specific transcription of human and rodent ubiquitous 5-aminolevulinate synthase (ALAS1) genes. Biochim Biophys Acta. 2001 Mar 19;1518(1-2):95-105. (
  • Roberts AG, Redding SJ, Llewellyn DH. An alternatively-spliced exon in the 5'-UTR of human ALAS1 mRNA inhibits translation and renders it resistant to haem-mediated decay. FEBS Lett. 2005 Feb 14;579(5):1061-6. (
  • Sadlon TJ, Dell'Oso T, Surinya KH, May BK. Regulation of erythroid 5-aminolevulinate synthase expression during erythropoiesis. Int J Biochem Cell Biol. 1999 Oct;31(10):1153-67. Review. (
  • Thunell S. Porphyrins, porphyrin metabolism and porphyrias. I. Update. Scand J Clin Lab Invest. 2000 Nov;60(7):509-40. 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: July 2009
Published: January 27, 2015