NaQPT2_candidate_QPT_1 is the second current NICAT quinolinate phosphoribosyltransferase candidate in the duplicated pyridine branch of nicotine biosynthesis. Like QPT_0, it is a credible NAD-pathway enzyme and a plausible nicotine-associated paralog, but the specialized copy is not yet resolved.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004514 nicotinate-nucleotide diphosphorylase (carboxylating) activity | IEA GO_REF:0000120 | ACCEPT | Summary: This is the correct catalytic activity for QPT_1. Reason: The accession is consistently identified as a quinolinate phosphoribosyltransferase family protein. Supporting Evidence: file:NICAT/NaQPT2_candidate_QPT_1/NaQPT2_candidate_QPT_1-notes.md UniProt curates A0A1J6IKI8 as nicotinate-nucleotide diphosphorylase (carboxylating), the quinolinate phosphoribosyltransferase/NadC chemistry that links quinolinate to NAD and nicotine pathway annotations. |
| GO:0005737 cytoplasm | IEA GO_REF:0000118 | KEEP AS NON CORE | Summary: Cytoplasmic localization is reasonable but peripheral. Reason: This location is plausible for QPT chemistry, but the important unresolved issue is whether QPT_1 is the pathway-specialized paralog. |
| GO:0009435 NAD+ biosynthetic process | IEA GO_REF:0000120 | ACCEPT | Summary: QPT_1 belongs in NAD biosynthesis. Reason: This step converts quinolinate into a de novo NAD precursor and therefore clearly belongs in the NAD pathway. Supporting Evidence: file:NICAT/NaQPT2_candidate_QPT_1/NaQPT2_candidate_QPT_1-notes.md UniProt curates A0A1J6IKI8 as nicotinate-nucleotide diphosphorylase (carboxylating), the quinolinate phosphoribosyltransferase/NadC chemistry that links quinolinate to NAD and nicotine pathway annotations. |
| GO:0009611 response to wounding | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: This automated response term is plausible but not a core conclusion for QPT_1. Reason: Keep the annotation as a contextual inference rather than a central functional claim for this candidate. |
| GO:0016763 pentosyltransferase activity | IEA GO_REF:0000002 | MODIFY | Summary: This is too broad relative to the specific catalytic activity already assigned. Reason: QPT_1 has a specific phosphoribosyltransferase annotation that should be preferred over the generic pentosyltransferase parent. Proposed replacements: nicotinate-nucleotide diphosphorylase (carboxylating) activity |
| GO:0034213 quinolinate catabolic process | IEA GO_REF:0000118 | ACCEPT | Summary: This process term fits QPT_1 well. Reason: QPT chemistry consumes quinolinate and therefore belongs in quinolinate catabolism. |
| GO:0042179 nicotine biosynthetic process | IEA GO_REF:0000041 | KEEP AS NON CORE | Summary: QPT_1 is a plausible nicotine-pathway paralog, but the exact specialized copy remains unresolved. Reason: Family-level evidence and current UniProt annotation keep QPT_1 in scope, yet the available data still do not discriminate decisively between QPT_1 and QPT_0. Supporting Evidence: file:NICAT/NaQPT2_candidate_QPT_1/NaQPT2_candidate_QPT_1-notes.md QPT_1 remains a plausible NaQPT2 candidate, but the public annotations alone do not resolve whether it is the pathway-specialized copy versus QPT_0. |
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Download this section (compressed HTML)Q: Does QPT_1 show stronger nicotine-pathway induction or root specificity than QPT_0?
Q: Are both QPT paralogs catalytically redundant, or has one specialized for defense-associated nicotine production?
Experiment: Compare QPT_1 and QPT_0 catalytic properties and induction patterns under nicotine-promoting conditions.
Hypothesis: One QPT paralog is more tightly coupled to defense-associated nicotine biosynthesis.
Type: comparative biochemistry and expression profiling
Experiment: Measure the effect of selective QPT_1 disruption on NAD precursors and nicotine accumulation in roots.
Hypothesis: If QPT_1 is the specialized paralog, its loss will measurably reduce nicotine precursor flux.
Type: genetics plus metabolite profiling
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