NaUGT1 (g26396, annotated UGT85A2_0) is a Nicotiana attenuata family-1 UDP-glycosyltransferase that N-glucosylates nicotinic acid. This reaction activates the pyridine precursor for nicotine biosynthesis, supplying nicotinic acid N-glucoside to the A622 reductase and subsequent scaffold-forming reactions. Biochemical pathway reconstruction and genetic disruption support its contribution to nicotine production. The physiological roles of possible alternative acceptor substrates remain unresolved.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0008194 UDP-glycosyltransferase activity | IEA GO_REF:0000002 | ACCEPT | Summary: The protein is an active-family UDP-glycosyltransferase candidate with a UDP-glucose donor assignment. Reason: UDP-glycosyltransferase activity is a valid broad parent of the accepted UDP-glucosyltransferase function. The more specific donor assignment does not invalidate this broad InterPro inference. |
| GO:0035251 UDP-glucosyltransferase activity | IEA GO_REF:0000117 | MODIFY | Summary: The donor-specific parent can be refined to the demonstrated nicotinate N-glucosyltransferase reaction. Reason: GO:0050139 already exists for this exact reaction. The Cell 2026 NaUGT1 assay/perturbation primers map to the g26396 locus, and its primer-compatible extended ORF contains the complete A0A2H4GSI3 sequence. Independent tobacco UGT1 supplements explicitly map the assayed N-glucosyltransferase to a close homolog (466 identities across 485 alignment columns). This establishes gene-level function; the retrieved assays do not directly test the isolated 485-aa database form. Narrow the generic MF using the existing term rather than proposing a duplicate ontology term. Proposed replacements: nicotinate-N-glucosyltransferase activity Supporting Evidence: file:NICAT/NaUGT1_candidate_UGT85A2_0/NaUGT1_candidate_UGT85A2_0-bioinformatics/identity-cell.md Figure 3D assays purified recombinant NaUGT1 expressed in E. coli and detects nicotinic acid N-glucoside from nicotinic acid. file:NICAT/NaUGT1_candidate_UGT85A2_0/NaUGT1_candidate_UGT85A2_0-bioinformatics/RESULTS.md The assayed tobacco UGT1 maps explicitly to A0A1S3YWH6 and is a nicotinate N-glucosyltransferase. |
| GO:0080043 quercetin 3-O-glucosyltransferase activity | IEA GO_REF:0000118 | UNDECIDED | Summary: The nicotinate reaction is supported, but this additional acceptor-specific activity remains unresolved. Reason: Primary 2026 data support nicotinate N-glucosylation at the mapped g26396 locus, with a documented construct-boundary caveat. They do not assay every alternative acceptor. Neither the positive nicotine function nor sequence-family distance establishes that quercetin or 7-deoxyloganetic acid cannot also be glucosylated. The earlier reports wrongly used missing assays and automated homolog names as negative biochemical evidence. Retain the source assertion for substrate-panel adjudication rather than asserting a negative function. Supporting Evidence: file:NICAT/NaUGT1_candidate_UGT85A2_0/NaUGT1_candidate_UGT85A2_0-bioinformatics/identity-cell.md Figure 3D assays purified recombinant NaUGT1 expressed in E. coli and detects nicotinic acid N-glucoside from nicotinic acid. file:NICAT/NaUGT1_candidate_UGT85A2_0/NaUGT1_candidate_UGT85A2_0-bioinformatics/RESULTS.md The assayed tobacco UGT1 maps explicitly to A0A1S3YWH6 and is a nicotinate N-glucosyltransferase. |
| GO:0080044 quercetin 7-O-glucosyltransferase activity | IEA GO_REF:0000118 | UNDECIDED | Summary: The nicotinate reaction is supported, but this additional acceptor-specific activity remains unresolved. Reason: Primary 2026 data support nicotinate N-glucosylation at the mapped g26396 locus, with a documented construct-boundary caveat. They do not assay every alternative acceptor. Neither the positive nicotine function nor sequence-family distance establishes that quercetin or 7-deoxyloganetic acid cannot also be glucosylated. The earlier reports wrongly used missing assays and automated homolog names as negative biochemical evidence. Retain the source assertion for substrate-panel adjudication rather than asserting a negative function. Supporting Evidence: file:NICAT/NaUGT1_candidate_UGT85A2_0/NaUGT1_candidate_UGT85A2_0-bioinformatics/identity-cell.md Figure 3D assays purified recombinant NaUGT1 expressed in E. coli and detects nicotinic acid N-glucoside from nicotinic acid. file:NICAT/NaUGT1_candidate_UGT85A2_0/NaUGT1_candidate_UGT85A2_0-bioinformatics/RESULTS.md The assayed tobacco UGT1 maps explicitly to A0A1S3YWH6 and is a nicotinate N-glucosyltransferase. |
| GO:0102970 7-deoxyloganetic acid glucosyltransferase activity | IEA GO_REF:0000003 | UNDECIDED | Summary: The nicotinate reaction is supported, but this additional acceptor-specific activity remains unresolved. Reason: Primary 2026 data support nicotinate N-glucosylation at the mapped g26396 locus, with a documented construct-boundary caveat. They do not assay every alternative acceptor. Neither the positive nicotine function nor sequence-family distance establishes that quercetin or 7-deoxyloganetic acid cannot also be glucosylated. The earlier reports wrongly used missing assays and automated homolog names as negative biochemical evidence. Retain the source assertion for substrate-panel adjudication rather than asserting a negative function. Supporting Evidence: file:NICAT/NaUGT1_candidate_UGT85A2_0/NaUGT1_candidate_UGT85A2_0-bioinformatics/identity-cell.md Figure 3D assays purified recombinant NaUGT1 expressed in E. coli and detects nicotinic acid N-glucoside from nicotinic acid. file:NICAT/NaUGT1_candidate_UGT85A2_0/NaUGT1_candidate_UGT85A2_0-bioinformatics/RESULTS.md The assayed tobacco UGT1 maps explicitly to A0A1S3YWH6 and is a nicotinate N-glucosyltransferase. |
| GO:0042179 nicotine biosynthetic process | IDA PMID:41928514 Complete biosynthesis of nicotine. | NEW | Summary: NaUGT1 directly catalyzes the activating nicotinate N-glucosylation step in nicotine biosynthesis. Reason: Reinstate the prior author proposal with primary biochemical evidence and verified gene-level identity rather than the earlier notes-only TAS. NaUGT1 itself catalyzes an on-pathway reaction, established by recombinant assay and pathway reconstruction, independently of knockout necessity evidence. Supplemental primers map to g26396; the inferred N-terminal extension relative to the cached protein is documented, and no unverified isoform identifier is invented. QuickGO confirms the process definition/parents and analogous annotations on PMT1, PMT3, QPT2 and A622. No redundant process ancestor/descendant or GO-CAM assignment exists on this target. Supporting Evidence: file:NICAT/NaUGT1_candidate_UGT85A2_0/NaUGT1_candidate_UGT85A2_0-bioinformatics/identity-cell.md Figure 3D assays purified recombinant NaUGT1 expressed in E. coli and detects nicotinic acid N-glucoside from nicotinic acid. file:NICAT/NaUGT1_candidate_UGT85A2_0/NaUGT1_candidate_UGT85A2_0-bioinformatics/RESULTS.md The assayed tobacco UGT1 maps explicitly to A0A1S3YWH6 and is a nicotinate N-glucosyltransferase. |
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Download this section (compressed HTML)Q: Does the 45-residue N-terminal extension specified by the Cell 2026 cloning primers represent the dominant native g26396 protein, a corrected gene model, or a construct-specific choice? What activity does the isolated 485-aa A0A2H4GSI3 form retain?
Q: Does NaUGT1 also glucosylate quercetin or 7-deoxyloganetic acid under physiological conditions, and how selective is it for nicotinate relative to these acceptors?
Experiment: Compare the primer-compatible 530-aa construct and the 485-aa database form with nicotinate, quercetin and 7-deoxyloganetic acid, using product-resolved assays and matched protein amounts.
Hypothesis: The mapped gene product catalyzes nicotinate N-glucosylation; N-terminal sequence and alternative-acceptor contributions remain unresolved.
Type: comparative biochemical substrate assay
Experiment: Resolve the endogenous g26396 translation start with transcript-boundary sequencing and N-terminal proteomics in induced roots.
Hypothesis: The published cloning primers identify an upstream initiation site whose native usage has not been established by the retrieved assays.
Type: gene-model and isoform verification
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