Porphobilinogen synthase
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porphobilinogen synthase
EC 4.2.1.24; systematic name: 5-aminolevulinate hydro-lyase (adding 5-aminolevulinate and cyclizing); other names: δ-aminolevulinic acid dehydratase (abbr.: ALAD); aminolevulinate dehydratase. An enzyme that catalyses the conversion of two moles of 5-aminolevulinate to one mole of porphobilinogen + 2 H2O in the pathway for the synthesis of porphyrins. It is an abundant cytosolic homooctamer in mammalian cells. Each subunit contains a sulfhydryl group and a Zn atom. The crystal structure of the yeast enzyme consists of a TIM barrel. ALAD is identical with the 24 kDa proteasome inhibitor. Enzyme deficiency leads to a rare form of neurovisceral porphyria.
| porphobilinogen, porphin, porous | |
| porphyr+, porphyria, porphyrin |
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Porphobilinogen synthase
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Porphobilinogen synthase
| porphobilinogen synthase | |||||||
|---|---|---|---|---|---|---|---|
| Identifiers | |||||||
| EC number | 4.2.1.24 | ||||||
| CAS number | 9036-37-7 | ||||||
| Databases | |||||||
| IntEnz | IntEnz view | ||||||
| BRENDA | BRENDA entry | ||||||
| ExPASy | NiceZyme view | ||||||
| KEGG | KEGG entry | ||||||
| MetaCyc | metabolic pathway | ||||||
| PRIAM | profile | ||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||
| Gene Ontology | AmiGO / EGO | ||||||
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| Delta-aminolevulinic acid dehydratase | |
|---|---|
| Identifiers | |
| Symbol | ALAD |
| Entrez | 210 |
| HUGO | 395 |
| OMIM | 125270 |
| RefSeq | NM_001003945 |
| UniProt | P13716 |
| Other data | |
| EC number | 4.2.1.24 |
| Locus | Chr. 9 q32 |
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| high resolution crystal structure of a mg2-dependent 5-aminolevulinic acid dehydratase | |||||||||
| Identifiers | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Symbol | ALAD | ||||||||
| Pfam | PF00490 | ||||||||
| Pfam clan | CL0036 | ||||||||
| InterPro | IPR001731 | ||||||||
| PROSITE | PDOC00153 | ||||||||
| SCOP | 1aw5 | ||||||||
| SUPERFAMILY | 1aw5 | ||||||||
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Porphobilinogen synthase (or ALA dehydratase, or aminolevulinate dehydratase) synthesizes porphobilinogen through the asymmetric condensation of two molecules of aminolevulinic acid. All natural tetrapyrroles, including hemes, chlorophylls and vitamin B12, share porphobilinogen as a common precursor.
It catalyzes the second step of the biosynthesis of porphyrin. The porphobilinogen synthase catalyzed reaction is the first common step in the biosynthesis of all biological tetrapyrroles.
Porphobilinogen synthase is the prototype morpheein.
Deficiency
A deficiency of porphobilinogen synthase is usually acquired (rather than hereditary) and can be caused by heavy metal poisoning, especially lead poisoning, as the enzyme is very susceptible to inhibition by heavy metals.[1]
Hereditary insufficiency of porphobilinogen synthase is called porphobilinogen synthase (or ALA dehydratase) deficiency poprhyria. It is an extremely rare cause of porphyria,[2] with less than 10 cases ever reported.[3]
Heme synthesis—note that some reactions occur in the cytoplasm and some in the mitochondrion (yellow)
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Lead poisoning works on the cellular level by binding to this enzyme, rendering it useless.
References
- ^ ALA dehydratase reaction, from NetBiochem at the University of Utah. Last modified 1/5/95
- ^ Jaffe EK, Stith L (February 2007). "ALAD porphyria is a conformational disease". Am. J. Hum. Genet. 80 (2): 329–37. doi:10.1086/511444. PMC 1785348. PMID 17236137. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1785348. Retrieved 2008-12-10.
- ^ Overview of the Porphyrias at The Porphyrias Consortium (a part of NIH Rare Diseases Clinical Research Network (RDCRN)) Retrieved June 2011
External links
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