Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
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Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
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Query: EC:2.6.1.44 (
AGT
)
770
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
At least two glyoxylate aminotransferases are hypothesized to participate in the steps of photorespiration located in peroxisomes. Until recently, however, genes encoding these enzymes had not been identified. We describe the isolation and characterization of an alanine : glyoxylate aminotransferase (
AGT1
, formerly
AGT
) cDNA from Arabidopsis thaliana. Southern blot analysis confirmed that Arabidopsis
AGT1
is encoded by a single gene. Homologs of this class IV aminotransferase are also known in other plants, animals, and methylotrophic bacteria, suggesting an ancient evolutionary origin of this enzyme.
AGT1
transcripts were present in all tissues of Arabidopsis, but were most abundant in green, leafy tissues. Purified, recombinant Arabidopsis
AGT1
expressed in Escherichia coli catalyzed three transamination reactions using the following amino donor : acceptor combinations: alanine : glyoxylate, serine : glyoxylate, and serine : pyruvate.
AGT1
had the highest specific activity with the serine : glyoxylate transamination, and apparent Km measurements indicate that this is the preferred in vivo reaction. In vitro import experiments and subcellular fractionations localized
AGT1
to peroxisomes. Sequence analysis of the photorespiratory sat mutants revealed a single nucleotide substitution in the
AGT1
gene from these plants. This transition mutation is predicted to result in a proline-to-leucine substitution at residue 251 of
AGT1
. When this mutation was engineered into the recombinant
AGT1
protein, enzymatic activity using all three donor : acceptor pairs was abolished. We conclude that Arabidopsis
AGT1
is a peroxisomal photorespiratory enzyme that catalyzes transamination reactions with multiple substrates.
...
PMID:Peroxisomal alanine : glyoxylate aminotransferase (AGT1) is a photorespiratory enzyme with multiple substrates in Arabidopsis thaliana. 1130 39
