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 β-semialdehyde into carboxyspermidine in
an NADPH-dependent manner"]
No direct KT2440 PP_2928 enzyme assay is available, so the assignment remains ISS.
Re-read every existing annotation, core function, raw UniProt record, relevant
provider report and primary literature. Original annotation payloads and raw
UniProt/GOA snapshots were preserved; no new annotation rows were added. Five
authored NEW rows across the four-gene baseline remain inherited proposals, not
new proposals from this audit. Default Falcon research was attempted with
just deep-research ORGANISM GENE --provider falcon; it failed with HTTP 403
authentication. No provider report was fabricated or overwritten. Manual findings
are recorded here; the command logs are in the ignored module-audit cache.
QuickGO on 2026-11-05 confirmed active GO:0102143 includes both carboxynorspermidine
and carboxyspermidine dehydrogenase reactions, and GO:0102144 is obsolete as the
same activity. Searches for carboxyspermidine/carboxynorspermidine decarboxylase
and carboxypolyamine returned no specific decarboxylase term. The existing NTR
name was retained; no GO or PTN identifier was invented. PANTHER official names
were checked in panther.obo, and exact protein/subfamily assignments against the
unchanged UniProt records (PTHR43796:SF2 for the dehydrogenases; PTHR43727:SF1 for
the decarboxylases).
The comparative literature requires a substrate-specific reading. The B. fragilis
and C. leptum enzymes have measured putrescine/DAP kinetics, but these are not
measurements of this target [PMID:37437886, "These data suggest that both enzymes
can use putrescine or DAP and thus produce carboxyspermidine or
carboxynorspermidine."]. Agmatine was not tested in those comparisons. The 2025
reconstruction shows that related pairs can make tetramines or use agmatine;
those functions are not transferred here [PMID:40074085, "The ASA-dependent
pathway consisting of CASDH/CASDC homologs has diversified during evolution
to produce norspermidine (29), N1-aminopropylagmatine (37), and as we have shown
here, spermidine and Spm/Tspm."]. Physiological product identity, reconstructed
pathway activity and isolated-enzyme turnover are distinct evidence.
Targeted searches for PP_2928/carboxyspermidine and nspC/KT2440 did not recover
a direct target assay. The paired pathway remains a comparative proposal.
Family identity and adjacency are supportive but insufficient to establish
native diamine preference, particularly after CAPA-pathway diversification
PMID:37878710. The H. pylori putrescine assay cited previously cannot establish
physiological substrate preference: that homolog was also characterized as CAPADH.
No new PLP-binding or homodimerization row was added solely from family architecture;
the specific catalytic proposal already captures the core activity.