Heme Biosynthesis (Canis familiaris)

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delta-aminolevulinatesuccinyl-CoA + glycineBlack - reactantsdelta-aminolevulinateH+rate limiting stepRed - side productsFe2+protoporphyrinogen IXPPOXH2O2O2protohemeuroporphyrinogen IIIcoproporphyrinogen IIIhydroxymethylbilaneH2OCPOXO2H2OCO2URODFECHporphobilinogenCO2HMBSALAS2UROSCoAALADPorphobilinogenALAS1protoporphyrin IXCO2NH3H2O


The enzymatic process that produces heme is properly called porphyrin synthesis, as all the intermediates are tetrapyrroles that are chemically classified are porphyrins. The process is highly conserved across biology. In humans, this pathway serves almost exclusively to form heme. In other species, it also produces similar substances such as cobalamin (vitamin B12).

The pathway is initiated by the synthesis of D-Aminolevulinic acid (dALA or δALA) from the amino acid glycine and succinyl-CoA from the citric acid cycle (Krebs cycle). The rate-limiting enzyme responsible for this reaction, ALA synthase, is strictly regulated by intracellular iron levels and heme concentration. A low-iron level, e.g., in iron deficiency, leads to decreased porphyrin synthesis, which prevents accumulation of the toxic intermediates. This mechanism is of therapeutic importance: infusion of heme arginate or hematin can abort attacks of porphyria in patients with an inborn error of metabolism of this process, by reducing transcription of ALA synthase.

The organs mainly involved in heme synthesis are the liver and the bone marrow, although every cell requires heme to function properly. Heme is seen as an intermediate molecule in catabolism of haemoglobin in the process of bilirubin metabolism.

Source: Wikipedia http://en.wikipedia.org/wiki/Heme


This pathway was inferred from Homo sapiens pathway WP561(r21860) with a 53% conversion rate.

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106030view11:55, 16 August 2019MaintBotHMDB identifier normalization
89920view13:33, 6 October 2016MkutmonModified description
88636view14:50, 12 August 2016JmeliusOntology Term : 'heme biosynthetic pathway' added !
71972view00:16, 24 October 2013MaintBotremoved data source from nodes without identifier
70006view23:34, 11 July 2013MaintBotupdated to 2013 schema
40670view21:49, 1 March 2011MaintBotRemoved redundant pathway information and comments
35293view22:54, 11 February 2010Mills42Modified description
33961view18:25, 9 December 2009MaintBotAutomatic update of empty xrefs
31719view11:54, 14 August 2009MaintBotFixed group labels
30655view22:35, 29 July 2009MaintBotNew pathway

External references


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NameTypeDatabase referenceComment
ALADGeneProduct474808 (Entrez Gene)
ALAS1GeneProduct476600 (Entrez Gene)
ALAS2GeneProduct491498 (Entrez Gene)
CO2MetaboliteHMDB01967 (HMDB)
CoAMetaboliteHMDB01423 (HMDB)
FECHGeneProduct610360 (Entrez Gene)
H2O2MetaboliteHMDB03125 (HMDB)
H2OMetaboliteHMDB02111 (HMDB)
HMBSGeneProduct489373 (Entrez Gene)
NH3MetaboliteHMDB00051 (HMDB)
O2MetaboliteHMDB01377 (HMDB)
PPOXGeneProduct478980 (Entrez Gene)
PorphobilinogenMetaboliteHMDB00245 (HMDB)
URODGeneProduct475378 (Entrez Gene)
UROSGeneProduct492116 (Entrez Gene)
coproporphyrinogen IIIMetabolite
protoporphyrin IXMetabolite
uroporphyrinogen IIIMetabolite

Annotated Interactions

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