| EC |
2.5.1.61 |
| Accepted name: |
hydroxymethylbilane synthase |
| Reaction: |
4 porphobilinogen + H2O = hydroxymethylbilane + 4 NH3 |
|
For diagram of the early stages of porphyrin biosynthesis, click here |
| Other name(s): |
HMB-synthase; porphobilinogen deaminase; pre-uroporphyrinogen synthase; uroporphyrinogen I synthase; uroporphyrinogen I synthetase; uroporphyrinogen synthase; uroporphyrinogen synthetase; porphobilinogen ammonia-lyase (polymerizing); (4-[2-carboxyethyl]-3-[carboxymethyl]pyrrol-2-yl)methyltransferase (hydrolysing) |
| Systematic name: |
porphobilinogen:(4-[2-carboxyethyl]-3-[carboxymethyl]pyrrol-2-yl)methyltransferase (hydrolysing) |
| Comments: |
The enzyme works by stepwise addition of pyrrolylmethyl groups until a hexapyrrole is present at the active centre. The terminal tetrapyrrole is then hydrolysed to yield the product, leaving a cysteine-bound dipyrrole on which assembly continues. In the presence of a second enzyme, EC 4.2.1.75 uroporphyrinogen-III synthase, which is often called cosynthase, the product is cyclized to form uroporphyrinogen-III. If EC 4.2.1.75 is absent, the hydroxymethylbilane cyclizes spontaneously to form uroporphyrinogen I. |
| Links to other databases: |
BRENDA, EXPASY, Gene, KEGG, MetaCyc, PDB, CAS registry number: 9074-91-3 |
| References: |
| 1. |
Battersby, A.R., Fookes, C.J.R., Matcham, G.W.J. and McDonald, E. Biosynthesis of the pigments of life: formation of the macrocycle. Nature 285 (1980) 17–21. [PMID: 6769048] |
| 2. |
Frydman, R.B. and Feinstein, G. Studies on porphobilinogen deaminase and uroporphyrinogen 3 cosynthase from human erythrocytes. Biochim. Biophys. Acta 350 (1974) 358–373. [DOI] [PMID: 4847568] |
| 3. |
Levin, E.Y. and Coleman, D.L. The enzymatic conversion of porphobilinogen to uroporphyrinogen catalyzed by extracts of hematopoietic mouse spleen. J. Biol. Chem. 242 (1967) 4247–4253. [PMID: 6061709] |
| 4. |
Warren, M.J. and Jordan, P.M. Investigation into the nature of substrate binding to the dipyrromethane cofactor of Escherichia coli porphobilinogen deaminase. Biochemistry 27 (1988) 9020–9030. [PMID: 3069132] |
| 5. |
Miller, A.D., Hart, G.J., Packman, L.C. and Battersby, A.R. Evidence that the pyrromethane cofactor of hydroxymethylbilane synthase (porphobilinogen deaminase) is bound to the protein through the sulphur atom of cysteine-242. Biochem. J. 254 (1988) 915–918. [PMID: 3196304] |
| 6. |
Battersby, A.R. Tetrapyrroles: the pigments of life. Nat. Prod. Rep. 17 (2000) 507–526. [PMID: 11152419] |
|
| [EC 2.5.1.61 created 1972 as EC 4.3.1.8, transferred 2003 to EC 2.6.1.61] |
| |
|
| |
|
Printable version