PROSITE documentation PDOC00461
Porphobilinogen deaminase cofactor-binding site


Porphobilinogen deaminase (EC, or hydroxymethylbilane synthase, is an enzyme involved in the biosynthesis of porphyrins and related macrocycles. It catalyzes the assembly of four porphobilinogen (PBG) units in a head to tail fashion to form hydroxymethylbilane.

The enzyme covalently binds a dipyrromethane cofactor to which the PBG subunits are added in a stepwise fashion. In the Escherichia coli enzyme (gene hemC), this cofactor has been shown [1] to be bound by the sulfur atom of a cysteine. The region around this cysteine is conserved in porphobilinogen deaminases from various prokaryotic and eukaryotic sources.

Last update:

December 2004 / Pattern and text revised.


Technical section

PROSITE method (with tools and information) covered by this documentation:

PORPHOBILINOGEN_DEAM, PS00533; Porphobilinogen deaminase cofactor-binding site  (PATTERN)


1AuthorsMiller A.D. Hart G.J. Packman L.C. Battersby A.R.
TitleEvidence that the pyrromethane cofactor of hydroxymethylbilane synthase (porphobilinogen deaminase) is bound to the protein through the sulphur atom of cysteine-242.
SourceBiochem. J. 254:915-918(1988).
PubMed ID3196304

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