purB

UniProt ID: Q88FR7
Organism: Pseudomonas putida (strain ATCC 47054 / DSM 6125 / CFBP 8728 / NCIMB 11950 / KT2440)
Review Status: DRAFT
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Gene Description

PurB is a dual-function adenylosuccinate lyase. It cleaves SAICAR to AICAR and fumarate during IMP synthesis and cleaves adenylosuccinate to AMP and fumarate in the AMP branch.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0003824 catalytic activity
IEA
GO_REF:0000002 		MODIFY
Summary: Correct but less informative than the two enzyme-specific activities.
Reason: Replace the generic catalytic parent with both physiological PurB lyase activities.
GO:0004018 N6-(1,2-dicarboxyethyl)AMP AMP-lyase (fumarate-forming) activity
IEA
GO_REF:0000120 		ACCEPT
Summary: Correct enzyme-specific molecular function.
Reason: The exact Adenylosuccinate lyase product assignment supports this activity.
GO:0005829 cytosol
IEA
GO_REF:0000118 		KEEP AS NON CORE
Summary: Plausible electronic localization that is not core to either lyase activity.
Reason: Cytosol is consistent with a soluble bacterial metabolic enzyme, but no direct localization evidence was found.
GO:0006188 IMP biosynthetic process
IEA
GO_REF:0000002 		MODIFY
Summary: Correct but broader than the specific de novo pathway assignment.
Reason: Replace the broad IMP process with de novo IMP biosynthesis.
GO:0009152 purine ribonucleotide biosynthetic process
IEA
GO_REF:0000120 		MODIFY
Summary: Correct but broader than the specific pathway assignment.
Reason: Replace the broad purine-ribonucleotide process with de novo IMP biosynthesis.
GO:0016829 lyase activity
IEA
GO_REF:0000117 		MODIFY
Summary: Correct but less informative than the two enzyme-specific lyase activities.
Reason: Replace the broad lyase parent with both physiological PurB activities.
GO:0070626 (S)-2-(5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxamido) succinate lyase (fumarate-forming) activity
IEA
GO_REF:0000116 		ACCEPT
Summary: Correct enzyme-specific molecular function.
Reason: The exact Adenylosuccinate lyase product assignment supports this activity.
GO:0006189 'de novo' IMP biosynthetic process
IEA
GO_REF:0000041 		ACCEPT
Summary: Correct pathway assignment.
Reason: This enzyme catalyzes a required reaction between PRPP and IMP.
GO:0044208 'de novo' AMP biosynthetic process
IEA
GO_REF:0000041 		ACCEPT
Summary: Correct second physiological pathway role.
Reason: PurB also cleaves adenylosuccinate in the AMP branch.

Core Functions

Converts SAICAR to AICAR and fumarate during de novo IMP synthesis.

Molecular Function:
(S)-2-(5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxamido) succinate lyase (fumarate-forming) activity
Directly Involved In:
'de novo' IMP biosynthetic process
Supporting Evidence:
  • file:PSEPK/purB/purB-uniprot.txt
    RecName: Full=Adenylosuccinate lyase

Converts adenylosuccinate to AMP and fumarate in de novo AMP synthesis.

Molecular Function:
N6-(1,2-dicarboxyethyl)AMP AMP-lyase (fumarate-forming) activity
Directly Involved In:
'de novo' AMP biosynthetic process
Supporting Evidence:
  • file:PSEPK/purB/purB-uniprot.txt
    RecName: Full=Adenylosuccinate lyase

References

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Suggested Experiments

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

📚 Additional Documentation

Notes

(purB-notes.md)

purB curation notes

  • UniProt identifies Q88FR7 as Adenylosuccinate lyase [file:PSEPK/purB/purB-uniprot.txt "RecName: Full=Adenylosuccinate lyase"].
  • Retain both physiological lyase activities: SAICAR cleavage in de novo IMP synthesis
    and adenylosuccinate cleavage in the AMP branch. Replace generic catalytic/lyase
    parents with both exact activities and broad IMP/purine processes with GO:0006189.

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