Strongly supported carboxyspermidine dehydrogenase candidate. PP_2928 is adjacent to nspC and belongs to the CASDH/CANSDH family. Comparative, domain, and synteny evidence predicts NADPH-dependent condensation of putrescine with aspartate semialdehyde to form carboxyspermidine; direct biochemical or genetic confirmation in KT2440 is not available.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0102143 carboxynorspermidine dehydrogenase activity | ISS file:projects/P_PUTIDA/deep-research/PSEPK__bacterial-carboxyspermidine-biosynthesis__ppu00330-deep-research-openscientist.md | NEW | Summary: Family, domain, protein-length, and nspC synteny evidence support CASDH/CANSDH activity, but no direct KT2440 assay is available. GO:0102143 has the current label "carboxynorspermidine dehydrogenase activity"; with putrescine as substrate, this family activity yields carboxyspermidine and is referred to as CASDH in this pathway. Supporting Evidence: file:PSEPK/PP_2928/PP_2928-uniprot.txt PANTHER; PTHR43796:SF2; CARBOXYNORSPERMIDINE SYNTHASE file:PSEPK/PP_2928/PP_2928-deep-research-openscientist.md |
| GO:0008295 spermidine biosynthetic process | ISS file:projects/P_PUTIDA/deep-research/PSEPK__bacterial-carboxyspermidine-biosynthesis__ppu00330-deep-research-openscientist.md | NEW | Summary: Adjacency to nspC and comparison with characterized bacterial pathways strongly support participation in the carboxyspermidine route to spermidine; this target-species pathway assignment remains inferential. Supporting Evidence: file:PSEPK/PP_2928/PP_2928-uniprot.txt PANTHER; PTHR43796:SF2; CARBOXYNORSPERMIDINE SYNTHASE |
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Download this section (compressed HTML)Q: Does purified PP_2928 preferentially produce carboxyspermidine from putrescine under physiological conditions?
Experiment: Test NADPH-dependent PP_2928 activity with putrescine and aspartate semialdehyde and identify the product by LC-MS.
Type: biochemical validation
What is not known β curated, literature-grounded statements of the open unknowns (the inverse of core functions).
Gap: PP_2928 has not been tested biochemically or genetically in KT2440, so its substrate preference and contribution to cellular spermidine production remain unconfirmed.
OPEN BIOLOGY
What is known: Exact PTHR43796:SF2 family membership, adjacency to nspC, and characterized orthologous CASDH/CANSDH pathways strongly support the assignment.
Significance: Direct validation would establish whether carboxyspermidine is the physiological product in KT2440.
What would resolve it: Assay purified PP_2928 with putrescine and aspartate semialdehyde and measure polyamine profiles after PP_2928 deletion and complementation.
Provenance (the field's own admissions):
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Download this section (compressed HTML)PP_2928/Q88IS1 is immediately adjacent to nspC and its exact UniProt record
places it in the CASDH-related PTHR43796:SF2 family with IPR005097. These
checkable family, length, and synteny observations support transfer of the
experimentally established alternative polyamine pathway, without relying on
the unreproducible sequence-identity percentages in the OpenScientist report.
The paired CANSDH/CANSDC route was established genetically in Vibrio cholerae,
and CASDH chemistry was characterized structurally and biochemically in
Helicobacter pylori. [PMID:19196710 "deletion of either CANSDC or the putative
CANSDH led to loss of sym-norspermidine and spermidine"; PMID:36283333 "CASDH
condenses putrescine and aspartate Ξ²-semialdehyde into carboxyspermidine in
an NADPH-dependent manner"]
No direct KT2440 PP_2928 enzyme assay is available, so the assignment remains ISS.
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