Heme Biosynthesis (Danio rerio)

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rate limiting stepBlack - reactantsdelta-aminolevulinatesuccinyl-CoA + glycineH+delta-aminolevulinateprotoporphyrinogen IXFe2+Red - side productsfechCO2H2OCO2zgc:110219O2H2O2CO2alas1HMBSO2alas2CoAcpoxcoproporphyrinogen IIIH2OhydroxymethylbilaneNH3ppoxurosuroporphyrinogen IIIprotoporphyrin IXurodH2OprotohemePorphobilinogenporphobilinogen


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



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

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106065view11:57, 16 August 2019MaintBotHMDB identifier normalization
89921view13:34, 6 October 2016MkutmonModified description
88638view14:51, 12 August 2016JmeliusOntology Term : 'heme biosynthetic pathway' added !
71976view00:26, 24 October 2013MaintBotremoved data source from nodes without identifier
71939view21:40, 23 October 2013EgonwConverted labels into Metabolite DataNodes.
71938view21:37, 23 October 2013EgonwSplit two metabolites in one Label into two grouped Metabolite DataNodes.
70148view21:34, 12 July 2013MaintBotupdated to 2013 schema
40777view22:15, 1 March 2011MaintBotRemoved redundant pathway information and comments
35295view22:56, 11 February 2010Mills42Modified description
34169view21:17, 9 December 2009MaintBotAutomatic update of empty xrefs
31911view12:50, 14 August 2009MaintBotFixed group labels
31024view01:11, 30 July 2009MaintBotNew pathway

External references


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NameTypeDatabase referenceComment
CO2MetaboliteHMDB01967 (HMDB)
CoAMetaboliteHMDB01423 (HMDB)
H2O2MetaboliteHMDB03125 (HMDB)
H2OMetaboliteHMDB02111 (HMDB)
NH3MetaboliteHMDB00051 (HMDB)
O2MetaboliteHMDB01377 (HMDB)
PorphobilinogenMetaboliteHMDB00245 (HMDB)
alas1GeneProduct64608 (Entrez Gene)
alas2GeneProduct64607 (Entrez Gene)
coproporphyrinogen IIIMetabolite
cpoxGeneProduct321294 (Entrez Gene)
fechGeneProduct58215 (Entrez Gene)
ppoxGeneProduct664750 (Entrez Gene)
protoporphyrin IXMetabolite
urodGeneProduct30617 (Entrez Gene)
uroporphyrinogen IIIMetabolite
urosGeneProduct404731 (Entrez Gene)
zgc:110219GeneProduct550338 (Entrez Gene)

Annotated Interactions

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