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Enzyme involved in purine synthesis
Phosphoribosylaminoimidazole carboxylase
Phosphoribosylaminoimidazole carboxylase octamer, Human
5-aminoimidazole ribonucleotide + CO2 5'-phosphoribosyl-4-carboxy-5-aminoimidazole + 2 H
In plants and fungi
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.
In Escherichia coli
In the bacteriumEscherichia coli the reaction is catalyzed in two steps carried out by two separate enzymes, PurK and PurE.
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.
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. PMID10074353.
Phosphoribosylaminoimidazole carboxylase octamer, Human
5'-phosphoribosyl-4-carboxy-5-aminoimidazole + 2 H
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