Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0000166 nucleotide binding	IEA GO_REF:0000104	KEEP AS NON CORE	Summary: Valid substrate binding, but not the core function of PurK. Reason: Nucleotide binding supports catalysis, while the enzyme-specific activity captures the core function.
GO:0004638 phosphoribosylaminoimidazole carboxylase activity	IEA GO_REF:0000120	MODIFY	Summary: The pathway position is correct, but the term describes direct AIR carboxylation. Reason: Replace the direct carboxylase activity with the specific PurK N5-CAIR synthetase activity. Proposed replacements: 5-(carboxyamino)imidazole ribonucleotide synthase activity
GO:0005524 ATP binding	IEA GO_REF:0000120	KEEP AS NON CORE	Summary: Valid substrate binding, but not the core function of PurK. Reason: ATP is consumed by the synthetase reaction, while the enzyme-specific activity captures the core function.
GO:0005829 cytosol	IEA GO_REF:0000118	KEEP AS NON CORE	Summary: Plausible electronic localization that is not core to the enzyme function. Reason: Cytosol is consistent with a soluble bacterial metabolic enzyme, but no direct localization evidence was found.
GO:0006189 'de novo' IMP biosynthetic process	IEA GO_REF:0000120	ACCEPT	Summary: Correct pathway assignment. Reason: This enzyme catalyzes a required reaction between PRPP and IMP.
GO:0034028 5-(carboxyamino)imidazole ribonucleotide synthase activity	IEA GO_REF:0000120	ACCEPT	Summary: Correct enzyme-specific molecular function. Reason: The exact N5-carboxyaminoimidazole ribonucleotide synthase product assignment supports this activity.
GO:0046872 metal ion binding	IEA GO_REF:0000002	KEEP AS NON CORE	Summary: Valid cofactor binding, but not the core function of PurK. Reason: Metal binding supports catalysis, while the enzyme-specific activity captures the core function.

Core Functions

Forms N5-CAIR in the first half of the bacterial AIR-carboxylation stage.

Molecular Function:

5-(carboxyamino)imidazole ribonucleotide synthase activity

Directly Involved In:

'de novo' IMP biosynthetic process

Supporting Evidence:

file:PSEPK/purK/purK-uniprot.txt
RecName: Full=N5-carboxyaminoimidazole ribonucleotide synthase
PMID:10574791
Conversion of 5-aminoimidazole ribonucleotide (AIR) to 4-carboxyaminoimidazole ribonucleotide (CAIR) in Escherichia coli requires two proteins - PurK and PurE.

References

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Suggested Experiments

Experiment: Test a clean purK deletion for purine auxotrophy and rescue by the appropriate downstream purine intermediate or by gene complementation.

📚 Additional Documentation

Notes

(purK-notes.md)

purK curation notes

UniProt identifies Q88C48 as N5-carboxyaminoimidazole ribonucleotide synthase [file:PSEPK/purK/purK-uniprot.txt "RecName: Full=N5-carboxyaminoimidazole ribonucleotide synthase"].
Bacterial AIR carboxylation requires PurK and PurE, with N5-CAIR as the PurK product
PMID:10574791.
Replace the direct AIR-carboxylase term with GO:0034028. Retain ATP, nucleotide,
and metal binding as non-core.

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