NaQPT2_candidate_QPT_0 is one of the two current NICAT quinolinate phosphoribosyltransferase candidates for the duplicated pyridine branch of nicotine biosynthesis. It clearly encodes a nicotinate-nucleotide diphosphorylase in NAD precursor metabolism, but the exact pathway-specialized paralog remains unresolved.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004514 nicotinate-nucleotide diphosphorylase (carboxylating) activity | IEA GO_REF:0000120 | ACCEPT | Summary: This is the core catalytic annotation for QPT_0. Reason: UniProt and the protein family assignment consistently identify the quinolinate phosphoribosyltransferase reaction. Supporting Evidence: file:NICAT/NaQPT2_candidate_QPT_0/NaQPT2_candidate_QPT_0-notes.md UniProt curates A0A1J6KEF3 as nicotinate-nucleotide diphosphorylase (carboxylating), the quinolinate phosphoribosyltransferase/NadC reaction that connects quinolinate metabolism to NAD and nicotine pathway annotations. |
| GO:0005737 cytoplasm | IEA GO_REF:0000118 | KEEP AS NON CORE | Summary: Cytoplasmic localization is plausible but not central to this review. Reason: Retain the location as reasonable contextual information while focusing on catalytic chemistry and paralog resolution. |
| GO:0009435 NAD+ biosynthetic process | IEA GO_REF:0000120 | ACCEPT | Summary: QPT_0 belongs in de novo NAD biosynthesis. Reason: The quinolinate phosphoribosyltransferase step is a standard part of the NAD pathway that underlies the nicotine pyridine branch. Supporting Evidence: file:NICAT/NaQPT2_candidate_QPT_0/NaQPT2_candidate_QPT_0-notes.md UniProt curates A0A1J6KEF3 as nicotinate-nucleotide diphosphorylase (carboxylating), the quinolinate phosphoribosyltransferase/NadC reaction that connects quinolinate metabolism to NAD and nicotine pathway annotations. |
| GO:0009611 response to wounding | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: This regulatory-context annotation is plausible but not strongly resolved for QPT_0 specifically. Reason: Nicotine-pathway genes are often inducible by damage cues, but the key curation issue here is enzymatic and paralog-specific rather than response biology. |
| GO:0016763 pentosyltransferase activity | IEA GO_REF:0000002 | MODIFY | Summary: This broader transferase term is directionally correct but should be replaced by the specific QPT activity term. Reason: GO:0004514 already captures the exact catalytic chemistry for this protein. Proposed replacements: nicotinate-nucleotide diphosphorylase (carboxylating) activity |
| GO:0034213 quinolinate catabolic process | IEA GO_REF:0000118 | ACCEPT | Summary: This process annotation fits the known QPT reaction. Reason: QPT converts quinolinate into nicotinate mononucleotide and therefore participates directly in quinolinate consumption. |
| GO:0042179 nicotine biosynthetic process | IEA GO_REF:0000041 | KEEP AS NON CORE | Summary: QPT_0 is a plausible nicotine-pathway candidate, but exact paralog assignment remains open. Reason: Family-level and UniProt evidence keep QPT_0 in scope for the nicotine pyridine branch, yet the current data do not conclusively rank it above QPT_1 as the specialized root copy. Supporting Evidence: file:NICAT/NaQPT2_candidate_QPT_0/NaQPT2_candidate_QPT_0-notes.md QPT_0 is therefore a plausible NaQPT2 candidate, but the current public record does not by itself establish whether QPT_0 or QPT_1 is the root nicotine-pathway-specialized paralog. |
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Download this section (compressed HTML)Q: Which of the two QPT paralogs is most strongly coupled to nicotine induction and root-enriched pathway expression?
Q: Do QPT_0 and QPT_1 differ in catalytic efficiency or tissue distribution enough to explain pathway specialization?
Experiment: Compare QPT_0 and QPT_1 enzymatic activity and transcript abundance across nicotine-inducing conditions in roots.
Hypothesis: One QPT paralog is specialized for the nicotine-associated pyridine branch.
Type: comparative biochemistry and expression profiling
Experiment: Perturb QPT_0 and QPT_1 individually and quantify quinolinate, nicotinate ribonucleotide, and nicotine levels in roots.
Hypothesis: The pathway-specialized QPT paralog will have a stronger effect on nicotine precursor supply.
Type: genetics plus metabolite profiling
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