Gene Ontology annotation through association of InterPro records with GO terms

InterPro2GO maps class-IV aminotransferase / BCAT family signatures to generic catalytic activity, BCAA:2-oxoglutarate transaminase activity and BCAA metabolic process; the latter two over-reach for the methionine-specialized BCAT4.

Annotation inferences using phylogenetic trees

PAINT IBA annotations transfer ancestral BCAA transaminase activity (PTN002450258) and cytosolic activity (PTN005130943, BCAT4/BCAT6 subclade) to BCAT4.

Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt

UniProt subcellular location "Cytoplasm" mapped to GO:0005737.

GO_REF:0000120

Combined Automated Annotation using Multiple IEA Methods

EC 2.6.1.88 / RHEA:31763 mapped to L-methionine:oxo-acid transaminase activity, consistent with experimental data.

GO_REF:0000122

AtSubP analysis

AtSubP predicts cytoplasmic localization, consistent with experiment.

PMID:17056707

Branched-chain aminotransferase4 is part of the chain elongation pathway in the biosynthesis of methionine-derived glucosinolates in Arabidopsis.

Recombinant BCAT4 prefers Met, homomethionine and their 2-oxo acids; Leu is converted with about 5-fold lower affinity and Ile/Val barely.

"Recombinant BCAT4 showed high efficiency with Met and its derivatives and the corresponding 2-oxo acids"
bcat4 knockouts have about 50% of wild-type Met-derived glucosinolates and accumulate Met and S-methylmethionine, placing BCAT4 at the initial Met deamination.

"This sharp increase of free Met and its transport derivative SMM further support the conclusion that BCAT4 catalyzes the initial transamination of Met in glucosinolate formation generating MTOB."
BCAT4 is cytosolic (GFP and fractionation), expressed in phloem, wound- and light-induced.

"BCAT4 transcription is induced by wounding and is predominantly observed in the phloem."

PMID:18318836

Cloning and functional characterization of Arabidopsis thaliana D-amino acid aminotransferase--D-aspartate behavior during germination.

Characterizes Arabidopsis D-amino acid aminotransferase; UniProt cites it for BCAT4 kinetic data (Km for L-Leu, lack of D-isomer activity), which cannot be verified from the cached abstract.

"This is the first report of cDNA cloning and functional characterization of a D-amino acid aminotransferase in eukaryotes."

PMID:12068099

The branched-chain amino acid transaminase gene family in Arabidopsis encodes plastid and mitochondrial proteins.

BCAT4 fails to complement a yeast bat1/bat2 BCAA auxotroph, even with a mitochondrial presequence, and lacks organellar targeting signals.

"No complementation was achieved with AtBCAT-4 (data not shown)."