NaQPT2_candidate_QPT_0 Notes

• UniProt curates A0A1J6KEF3 as nicotinate-nucleotide diphosphorylase (carboxylating), the quinolinate phosphoribosyltransferase/NadC reaction that connects quinolinate metabolism to NAD and nicotine pathway annotations. [file:NICAT/NaQPT2_candidate_QPT_0/NaQPT2_candidate_QPT_0-uniprot.txt "DE RecName: Full=nicotinate-nucleotide diphosphorylase (carboxylating)"; "CC -!- CATALYTIC ACTIVITY: Reaction=nicotinate beta-D-ribonucleotide + CO2 + diphosphate = quinolinate + 5-phospho-alpha-D-ribose 1-diphosphate + 2 H(+)"; "CC -!- PATHWAY: Alkaloid biosynthesis; nicotine biosynthesis."; "CC -!- PATHWAY: Cofactor biosynthesis; NAD(+) biosynthesis; nicotinate D-ribonucleotide from quinolinate: step 1/1."]
• UniProt places this candidate in the NadC/ModD family and assigns both NAD+ biosynthetic process and nicotine biosynthetic process, which makes QPT_0 a strong biochemical candidate for the duplicated pyridine branch. [file:NICAT/NaQPT2_candidate_QPT_0/NaQPT2_candidate_QPT_0-uniprot.txt "CC -!- SIMILARITY: Belongs to the NadC/ModD family."; "DR GO; GO:0009435; P:NAD+ biosynthetic process; IEA:UniProtKB-UniPathway."; "DR GO; GO:0042179; P:nicotine biosynthetic process; IEA:UniProtKB-UniPathway."]
• The N. attenuata genome paper argues that nicotine biosynthesis emerged from duplicated NAD-pathway genes, which is the core rationale for reviewing multiple QPT paralogs instead of accepting both automatically. PMID:28536194
• The full glucosylation preprint keeps QPT2 tied to the modern nicotine module by listing it among the stronger tobacco genes correlated with UGT1, but that remains coexpression evidence rather than direct enzymology. [file:projects/NICOTINE_BIOSYNTHESIS/biorxiv-nicotine-glucosylation-notes.md "genes most correlated with UGT1 include BBLa, QPT2, beta-GD1, A622, PMT1, PMT2, PMT3, and MATE1"; "QPT2 and AO2 are supported at the level of coordinated pathway expression and pathway framing, but this paper does not directly assay their enzymatic roles."]
• 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. [file:NICAT/NaQPT2_candidate_QPT_0/NaQPT2_candidate_QPT_0-uniprot.txt "GN Name=QPT_0"; "CC -!- PATHWAY: Alkaloid biosynthesis; nicotine biosynthesis."]