AGT1 / SGAT (At2g13360, Q56YA5) curation notes

Deep research could not be run in this environment (no provider API keys). These notes are a
literature summary built only from cached publications (publications/PMID_*.md) and the UniProt
record (AGT1-uniprot.txt). No *-deep-research-*.md file exists for this gene.

Identity and family

• AGT1 (alanine:glyoxylate aminotransferase 1; serine:glyoxylate aminotransferase, SGAT) is a class
  V PLP-dependent aminotransferase, homolog of animal AGT1/AGXT, encoded by a single gene with a
  C-terminal PTS1 PMID:11309139. PANTHER PTHR21152:SF24; Pfam PF00266 (Aminotran_5).
• Crystal structure: homodimer, PLP bound non-covalently; residues Tyr35'/Arg36' from the partner
  subunit bind L-serine, unlike human/Anabaena AGT1 that prefer alanine PMID:31681359.

Activities (substrate breadth)

• Recombinant AGT1 catalyses Ala:glyoxylate, Ser:glyoxylate and Ser:pyruvate transamination, with
  Ser:glyoxylate preferred PMID:11309139.
• Native leaf SGAT: Ala:glyoxylate about 55% of Ser:glyoxylate rate; kinetic constants suggest Ala and
  Ser could be used similarly as amino donors PMID:18235971.
• Asparagine is an efficient donor (Vmax 5-20x higher than Ser/Ala); Asn induces AGT1 transcripts in
  roots PMID:23098902.

Judgement: L-serine:glyoxylate transaminase (GO:0050281) is the core photorespiratory activity, the
one whose loss in the sat mutants is lethal in air. Ala:glyoxylate (GO:0008453), Ser:pyruvate
(GO:0004760) and Asn:oxo-acid (GO:0047297) activities are real but non-core.

Localization

• Peroxisome by in vitro import and fractionation PMID:11309139; BiFC with RabGAP22 in peroxisomes
  PMID:24505423; abundant in leaf peroxisome proteome (PMID:17951448).
• Proteomic hits in chloroplast/stroma, mitochondrion, plasma membrane, apoplast and crude cytosol
  are treated as contamination.

Physiological role

• sat mutants lack SGAT activity, are inviable in air but normal at high CO2, and accumulate Ser and Gly
  PMID:16592821.
• The sat lesion is a P251L substitution in AGT1 that abolishes activity PMID:11309139.
• Role in the cycle: the SGAT step supplies the second amino group for glycine formation
  PMID:22303256.
• Non-photorespiratory roles: Asn catabolism (PMID:23098902); root development and salt tolerance in
  overexpressors (PMID:31161264, not cached; mentioned in UniProt only).

Annotation-specific notes

• Peroxisome EXP from PMID:24505423 (RabGAP22 paper): BiFC signal of the RabGAP22-AGT1 pair in
  peroxisomes of N. benthamiana. Supports peroxisomal localization; accepted.
• L-alanine:oxo-acid transaminase (GO:0047635, Rhea IEA) is the parent of GO:0008453; the Rhea reaction
  mapped (Asn + pyruvate = 2-oxosuccinamate + Ala) is a reversible transamination involving alanine.
  Non-core, like GO:0008453.

Module comparison (modules/photorespiration_c2_cycle.yaml, sgat_step)

Module asserts GO:0050281 / GO:0009853 / GO:0005777 for AGT1. This review agrees on all three.