Delta-aminolevulinic acid dehydratase

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Protein ALAD PDB 1e51.png
Available structures
PDB Ortholog search: PDBe RCSB
Aliases ALAD, ALADH, PBGS, aminolevulinate dehydratase
External IDs MGI: 96853 HomoloGene: 16 GeneCards: ALAD
Gene location (Human)
Chromosome 9 (human)
Chr. Chromosome 9 (human)[1]
Chromosome 9 (human)
Genomic location for ALAD
Genomic location for ALAD
Band 9q32 Start 113,386,317 bp[1]
End 113,401,333 bp[1]
RNA expression pattern
PBB GE ALAD 218487 at fs.png

PBB GE ALAD 218489 s at fs.png
More reference expression data
Species Human Mouse
RefSeq (mRNA)



RefSeq (protein)



Location (UCSC) Chr 9: 113.39 – 113.4 Mb Chr 9: 62.51 – 62.52 Mb
PubMed search [3] [4]
View/Edit Human View/Edit Mouse

Delta-aminolevulinic acid dehydratase is an enzyme (EC that in humans is encoded by the ALAD gene.[5][6] It catalyzes the following reaction:

2 δ-aminolevulinic acid porphobilinogen + 2 H2O

The ALAD enzyme is composed of 8 identical subunits and catalyzes the condensation of 2 molecules of delta-aminolevulinate to form porphobilinogen (a precursor of heme, cytochromes and other hemoproteins). ALAD catalyzes the second step in the porphyrin and heme biosynthetic pathway; zinc is essential for enzymatic activity. ALAD enzymatic activity is inhibited by lead, beginning at blood lead levels that were once considered to be safe (<10 μg/dL) and continuing to correlate negatively across the range from 5 to 95 μg/dL.[7] Inhibition of ALAD by lead leads to anemia primarily because it both inhibits heme synthesis and shortens the lifespan of circulating red blood cells, but also by stimulating the excessive production of the hormone erythropoietin, leading to inadequate maturation of red cells from their progenitors. A defect in the ALAD structural gene can cause increased sensitivity to lead poisoning and acute hepatic porphyria. Alternatively spliced transcript variants encoding different isoforms have been identified.[8]


  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000148218 - Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000028393 - Ensembl, May 2017
  3. ^ "Human PubMed Reference:". 
  4. ^ "Mouse PubMed Reference:". 
  5. ^ Eiberg H, Mohr J, Nielsen LS (Jun 1983). "delta-Aminolevulinatedehydrase: synteny with ABO-AK1-ORM (and assignment to chromosome 9)". Clin Genet. 23 (2): 150–4. PMID 6839527. doi:10.1111/j.1399-0004.1983.tb01864.x. 
  6. ^ Beaumont C; Foubert C; Grandchamp B; Weil D; Van Cong N'Guyen; Gross MS; Nordmann Y (Aug 1984). "Assignment of the human gene for delta aminolevulinate dehydrase to chromosome 9 by somatic cell hybridization and specific enzyme immunoassay". Ann Hum Genet. 48 (Pt 2): 153–9. PMID 6378062. doi:10.1111/j.1469-1809.1984.tb01010.x. 
  7. ^ Abadin H, Ashizawa A, Stevens YW, Llados F, Diamond G, Sage G, Citra M, Quinones A, Bosch SJ, Swarts SG (August 2007). Toxicological Profile for Lead (PDF). Atlanta, GA: Agency for Toxic Substances and Disease Registry (US). pp. 22, 30. PMID 24049859. Retrieved 22 November 2015. 
  8. ^ "Entrez Gene: ALAD aminolevulinate, delta-, dehydratase". 

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