NaA622 is the primary NICAT mapping for the late nicotine-pathway A622 oxidoreductase. The recent nicotine glucosylation preprint redefines the tobacco A622 ortholog as a nicotinic acid N-glucoside reductase (NaGR) in the four-enzyme nicotine synthase cascade, making this accession the leading candidate for the analogous late reductase step in Nicotiana attenuata.
Definition: Catalysis of the NADPH-dependent reduction of nicotinic acid N-glucoside to a reduced dihydropyridine glucoside intermediate in nicotine biosynthesis.
Justification: GO currently captures A622 only at the generic oxidoreductase level, whereas the recent pathway paper resolves a substrate-specific reductase activity for the A622 ortholog.
Parent term: oxidoreductase activity
Supporting Evidence:
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0016491 oxidoreductase activity | IEA GO_REF:0000002 | MARK AS OVER ANNOTATED | Summary: This annotation is directionally correct but much too generic for the current state of A622 biology. Reason: The glucosylation preprint resolves A622 as a specific late-pathway reductase acting on nicotinic acid N-glucoside, so the broad parent term no longer captures the informative chemistry of the protein. Supporting Evidence: file:NICAT/NaA622/NaA622-notes.md The full nicotine glucosylation preprint redefines A622 as NaGR, a nicotinic acid N-glucoside reductase in the four-enzyme nicotine synthase cascade, making A622 a directly supported late-pathway catalyst rather than a generic oxidoreductase placeholder. |
| GO:0042179 nicotine biosynthetic process | TAS file:NICAT/NaA622/NaA622-notes.md | NEW | Summary: A nicotine-biosynthetic-process annotation is now directly supported for the A622 orthologous role. Reason: The recent pathway reconstruction and knockout logic place A622/NaGR in the core late nicotine synthase cascade rather than as a loosely associated oxidoreductase. Supporting Evidence: file:NICAT/NaA622/NaA622-notes.md The full nicotine glucosylation preprint redefines A622 as NaGR, a nicotinic acid N-glucoside reductase in the four-enzyme nicotine synthase cascade, making A622 a directly supported late-pathway catalyst rather than a generic oxidoreductase placeholder. |
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Download this section (compressed HTML)Q: Does A0A314KUK7 account for most NaGR flux in Nicotiana attenuata roots, or is the alternate IFRH_0 paralog also catalytically competent in vivo?
Q: Is the attenuata A622 protein substrate-selective for nicotinic acid N-glucoside in the same way as the tobacco NaGR ortholog?
Experiment: Compare recombinant A0A314KUK7 and IFRH_0 proteins in side-by-side nicotinic acid N-glucoside reduction assays with NADPH.
Hypothesis: A0A314KUK7 is the dominant NICAT NaGR paralog.
Type: biochemical enzyme assay
Experiment: Knock out the primary A622 mapping in roots and profile nicotinic acid N-glucoside, downstream glucosides, and nicotine accumulation after topping or herbivory induction.
Hypothesis: Loss of the primary A622 paralog will block late-pathway flux upstream of nicotine.
Type: genetic perturbation plus metabolite profiling
The NaA622 gene in Nicotiana attenuata encodes an isoflavone reductase-like protein predominantly expressed in roots, suggesting a specialized role in root-specific metabolic processes, potentially linked to nicotine biosynthesis. While direct functional characterization in N. attenuata is lacking, domain analysis and comparative genomics provide valuable insights into its possible enzymatic functions.
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