porphobilinogen deaminase; PBG-D; hydroxymethylbilane synthase; HMBS; pre-uroporphyrinogen synthase (HMBS, PBGD, UPS)

Function

• tetrapolymerization of the monopyrrole porphobilinogen (PBG) into the hydroxymethylbilane pre-uroporphyrinogen in several discrete steps

4 porphobilinogen + H2O = hydroxymethylbilane + 4 NH3

• porphyrin metabolism; protoporphyrin-IX biosynthesis
• coproporphyrinogen-III from 5-aminolevulinate: step 2/4

Cofactor:

• binds 1 dipyrromethane group covalently
• the porphobilinogen subunits are added to the dipyrromethane group

Structure

belongs to the HMBS family

Compartment

cytoplasm (probable)

Alternative splicing

named isoforms=2

Expression

• isoform 1 is ubiquitously expressed
• isoform 2 is found only in erythroid cells

Pathology

• defects in HMBS are the cause of acute intermittent porphyria

More general terms

• ammonia lyase
• phosphoprotein

Additional terms

• heme synthesis

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=3145
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:3145
• OMIM: https://mirror.omim.org/entry/176000
• OMIM: https://mirror.omim.org/entry/609806
• UniProt: http://www.uniprot.org/uniprot/P08397.html