Phosphoribosylaminoimidazole carboxylase

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phosphoribosylaminoimidazole carboxylase
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 / EGO
phosphoribosylaminoimidazole carboxylase, phosphoribosylaminoimidazole succinocarboxamide synthetase
Identifiers
Symbol PAICS
Alt. symbols PAIS
Entrez 10606
HUGO 8587
OMIM 172439
RefSeq NM_006452
UniProt P22234
Other data
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 \rightleftharpoons 5'-phosphoribosyl-4-carboxy-5-aminoimidazole + 2 H+

In plants and fungi[edit]

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[edit]

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]

  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]

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