phosphoribosylaminoimidazole carboxylase

File:2h31a.jpg

Phosphoribosylaminoimidazole carboxylase oktamer, Human

Identifiers
EC number| 4.1.1.21
CAS number| 9032-04-6
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  / QuickGO
| Search

PMC| articles
PubMed| articles
NCBI| proteins
phosphoribosylaminoimidazole carboxylase, phosphoribosylaminoimidazole succinocarboxamide synthetase

Identifiers
Symbol| PAICS
Alt. symbols| PAIS
Entrez| 10606
HUGO| 8587
OMIM| 172439
RefSeq| NM_006452
UniProt| P22234
Other data
EC number| 4.1.1.21
Locus| Chr. 4 pter-q21

Phosphoribosylaminoimidazole carboxylase (or AIR carboxylase) is an enzyme involved in nucleotide biosynthesis and in particular in purine biosynthesis. It catalyzes the conversion of 5'-phosphoribosyl-5-aminoimidazole ("AIR") into 5'-phosphoribosyl-4-carboxy-5-aminoimidazole ("CAIR") as described in the reaction:

5-aminoimidazole ribonucleotide + CO2 <math>\rightleftharpoons</math> 5'-phosphoribosyl-4-carboxy-5-aminoimidazole + 2 H+

## Contents

* 1 In plants and fungi
* 2 In Escherichia coli
* 3 References
* 4 External links

## In plants and fungi

[edit | edit source]

Phosphoribosylaminoimidazole carboxylase is a fusion protein in plants and fungi, but consists of two non-interacting proteins in bacteria, PurK and PurE.

The crystal structure of PurE indicates a unique quaternary structure that confirms the octameric nature of the enzyme.[1]

## In Escherichia coli

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In the bacterium Escherichia coli the reaction is catalyzed in two steps carried out by two separate enzymes, PurK and PurE.

PurK, N5-carboxyaminoimidazole ribonucleotide synthetase, catalyzes the conversion of 5-aminoimidazole ribonucleotide ("AIR"), ATP, and bicarbonate to N5-carboxyaminoimidazole ribonucleotide ("N5-CAIR"), ADP, and Pi.

PurE, N5-carboxyaminoimidazole ribonucleotide mutase, converts N5-CAIR to CAIR, the sixth step of de novo purine biosynthesis. In the presence of high concentrations of bicarbonate, PurE is reported able to convert AIR to CAIR directly and without ATP. Some members of this family contain two copies of this domain.[2]

## References

[edit | edit source]

1. ↑ Ealick SE, Stubbe J, Kappock TJ, Mathews II (1999). "Crystal structure of Escherichia coli PurE, an unusual mutase in the purine biosynthetic pathway". Structure. 7 (11): 1395–1406. doi:10.1016/S0969-2126(00)80029-5. PMID 10574791.
2. ↑ Meyer E, Stubbe J, Kappock TJ, Osuji C (1999). "Evidence for the direct transfer of the carboxylate of N5-carboxyaminoimidazole ribonucleotide (N5-CAIR) to generate 4-carboxy-5-aminoimidazole ribonucleotide catalyzed by Escherichia coli PurE, an N5-CAIR mutase". Biochemistry. 38 (10): 3012–3018. doi:10.1021/bi9827159. PMID 10074353.

## External links

[edit | edit source]

* phosphoribosylaminoimidazole+carboxylase at the US National Library of Medicine Medical Subject Headings (MeSH)
* PAICS photo

This article incorporates text from the public domain Pfam and InterPro: IPR000031

* v
* t
* e

* Metabolism: amino acid metabolism
* nucleotide enzymes

Purine metabolism|

| Anabolism|

| R5P→IMP:|

* Ribose-phosphate diphosphokinase
* Amidophosphoribosyltransferase
* Phosphoribosylglycinamide formyltransferase
* AIR synthetase (FGAM cyclase)
* Phosphoribosylaminoimidazole carboxylase
* Phosphoribosylaminoimidazolesuccinocarboxamide synthase
* IMP synthase

|

IMP→AMP:|

* Adenylosuccinate synthase
* Adenylosuccinate lyase
* reverse
* AMP deaminase

IMP→GMP:|

* IMP dehydrogenase
* GMP synthase
* reverse
* GMP reductase

Nucleotide salvage|

* Hypoxanthine-guanine phosphoribosyltransferase
* Adenine phosphoribosyltransferase

Catabolism|

* Adenosine deaminase
* Purine nucleoside phosphorylase
* Guanine deaminase
* Xanthine oxidase
* Urate oxidase

Pyrimidine metabolism|

| Anabolism|

* CAD
* Carbamoyl phosphate synthase II
* Aspartate carbamoyltransferase
* Dihydroorotase

* Dihydroorotate dehydrogenase
* Orotidine 5'-phosphate decarboxylase/Uridine monophosphate synthetase

* CTP synthetase

Catabolism|

* Dihydropyrimidine dehydrogenase
* Dihydropyrimidinase/DPYS
* Beta-ureidopropionase/UPB1

Deoxyribonucleotides|

* Ribonucleotide reductase
* Nucleoside-diphosphate kinase
* DCMP deaminase
* Thymidylate synthase
* Dihydrofolate reductase

* v
* t
* e

Carbon-carbon lyases (EC 4.1)

4.1.1: Carboxy-lyases|

* Acetoacetate decarboxylase
* Adenosylmethionine decarboxylase
* Arginine decarboxylase
* Aromatic L-amino acid decarboxylase
* Glutamate decarboxylase
* Histidine decarboxylase
* Lysine decarboxylase
* Malonyl-CoA decarboxylase
* Ornithine decarboxylase
* Oxaloacetate decarboxylase
* Phosphoenolpyruvate carboxykinase
* Phosphoenolpyruvate carboxylase
* Phosphoribosylaminoimidazole carboxylase
* Pyrophosphomevalonate decarboxylase
* Pyruvate decarboxylase
* RuBisCO
* Uridine monophosphate synthetase/Orotidine 5'-phosphate decarboxylase
* Uroporphyrinogen III decarboxylase

4.1.2: Aldehyde-lyases|

* Fructose-bisphosphate aldolase
* Aldolase A
* Aldolase B
* Aldolase C
* 2-hydroxyphytanoyl-CoA lyase
* Threonine aldolase

4.1.3: Oxo-acid-lyases|

* Isocitrate lyase
* 3-hydroxy-3-methylglutaryl-CoA lyase

4.1.99: Other|

* Tryptophanase
* Photolyase
* CPD lyase
* Spore photoproduct lyase

* v
* t
* e

Enzymes

Activity|

* Active site
* Binding site
* Catalytic triad
* Oxyanion hole
* Enzyme promiscuity
* Catalytically perfect enzyme
* Coenzyme
* Cofactor
* Enzyme catalysis

Regulation|

* Allosteric regulation
* Cooperativity
* Enzyme inhibitor
* Enzyme activator

Classification|

* EC number
* Enzyme superfamily
* Enzyme family
* List of enzymes

Kinetics|

* Enzyme kinetics
* Eadie–Hofstee diagram
* Hanes–Woolf plot
* Lineweaver–Burk plot
* Michaelis–Menten kinetics

Types|

* EC1 Oxidoreductases (list)
* EC2 Transferases (list)
* EC3 Hydrolases (list)
* EC4 Lyases (list)
* EC5 Isomerases (list)
* EC6 Ligases (list)

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