NaAO2_candidate_AO_0 Notes

• UniProt curates A0A1J6KBX2 as an L-aspartate oxidase/NadB-family flavoprotein that catalyzes oxidation of L-aspartate to iminoaspartate, linking this candidate to the upstream NAD branch that feeds pyridine alkaloid biosynthesis. [file:NICAT/NaAO2_candidate_AO_0/NaAO2_candidate_AO_0-uniprot.txt "DE RecName: Full=L-aspartate oxidase"; "CC -!- CATALYTIC ACTIVITY: Reaction=L-aspartate + O2 = iminosuccinate + H2O2"; "CC -!- PATHWAY: Alkaloid biosynthesis."; "CC -!- PATHWAY: Cofactor biosynthesis; NAD(+) biosynthesis; iminoaspartate from L-aspartate (oxidase route): step 1/1."]
• UniProt also places this candidate in plastid/chloroplast and in the NadB subfamily, which supports conserved primary-metabolism chemistry but does not by itself prove that AO_0 is the pathway-specialized nicotine paralog. [file:NICAT/NaAO2_candidate_AO_0/NaAO2_candidate_AO_0-uniprot.txt "CC -!- SUBCELLULAR LOCATION: Plastid, chloroplast"; "CC -!- SIMILARITY: Belongs to the FAD-dependent oxidoreductase 2 family. NadB subfamily."]
• The N. attenuata genome paper argues that nicotine biosynthesis arose through stepwise duplications of ancient NAD and polyamine pathways, so multiple AO-like paralogs are expected and must be resolved explicitly rather than all being treated as core nicotine genes. PMID:28536194
• The full glucosylation preprint keeps AO-like chemistry in scope by placing AO2B among the stronger tobacco genes co-expressed with A622, but this is coexpression support rather than direct catalytic assignment and therefore does not resolve AO_0 versus AO_1 in NICAT. [file:projects/NICOTINE_BIOSYNTHESIS/biorxiv-nicotine-glucosylation-notes.md "genes most correlated with A622 include MATE1, PMT3, PMT2, PMT1, beta-GD1, AO2B, and MPO1"; "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."]
• AO_0 is therefore a plausible NaAO2 candidate, but the current public record does not distinguish it cleanly from AO_1 as the nicotine-pathway-specialized copy. [file:NICAT/NaAO2_candidate_AO_0/NaAO2_candidate_AO_0-uniprot.txt "GN Name=AO_0"; "CC -!- PATHWAY: Alkaloid biosynthesis."]