PurT is the ATP- and formate-dependent GAR transformylase that provides an alternative route from GAR to FGAR during de novo IMP synthesis. It occupies the same pathway position as folate-dependent PurN but uses free formate as the one-carbon donor.
| 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 PurT. Reason: Nucleotide binding supports catalysis, while the enzyme-specific activity captures the core function. |
| GO:0000287 magnesium ion binding | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: Valid cofactor binding, but not the core function of PurT. Reason: Magnesium supports catalysis, while the enzyme-specific activity captures the core function. |
| GO:0003824 catalytic activity | IEA GO_REF:0000117 | MODIFY | Summary: Correct but less informative than the enzyme-specific activity. Reason: Replace the generic catalytic parent with the formate-dependent PurT activity. Proposed replacements: phosphoribosylglycinamide formyltransferase 2 activity |
| GO:0004644 phosphoribosylglycinamide formyltransferase activity | IEA GO_REF:0000002 | REMOVE | Summary: Incorrect folate-dependent PurN chemistry assigned to PurT. Reason: PurT is a C-N ligase that uses ATP and free formate; GO:0004644 denotes the distinct folate-dependent transferase reaction. Supporting Evidence: file:PSEPK/purT/purT-uniprot.txt Reaction=N(1)-(5-phospho-beta-D-ribosyl)glycinamide + formate + ATP = |
| GO:0005524 ATP binding | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: Valid substrate binding, but not the core function of PurT. Reason: ATP is consumed by the ligase 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:0009152 purine ribonucleotide biosynthetic process | IEA GO_REF:0000002 | MODIFY | Summary: Correct but broader than the specific pathway assignment. Reason: Replace the broad purine-ribonucleotide process with de novo IMP biosynthesis. Proposed replacements: 'de novo' IMP biosynthetic process |
| GO:0016742 hydroxymethyl-, formyl- and related transferase activity | IEA GO_REF:0000002 | REMOVE | Summary: Incorrect transferase classification for the ATP-dependent PurT ligase reaction. Reason: PurT forms a carbon-nitrogen bond with ATP hydrolysis and is classified as EC 6.3.1.21, not as a formyl-group transferase. Supporting Evidence: file:PSEPK/purT/purT-uniprot.txt EC=6.3.1.21 |
| GO:0043815 phosphoribosylglycinamide formyltransferase 2 activity | IEA GO_REF:0000120 | ACCEPT | Summary: Correct enzyme-specific molecular function. Reason: The exact Formate-dependent phosphoribosylglycinamide formyltransferase 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 PurT. Reason: Metal binding supports catalysis, while the enzyme-specific activity captures the core function. |
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Download this section (compressed HTML)Q: Under which carbon and folate conditions does PurT rather than PurN provide most GAR transformylase flux?
Experiment: Test a clean purT deletion for purine auxotrophy and rescue by the appropriate downstream purine intermediate or by gene complementation.
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