Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.6.1.19 (GABA transaminase)
 808 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The gabCTDP gene cluster, which specifies and regulates synthesis of the gamma-aminobutyrate (GABA) transport carrier, of glutamate-succinic semialdehyde transaminase, and of succinic semialdehyde dehydrogenase, responsible for the uptake and metabolism of gamma-aminobutyric acid in Escherichia coli K-12, was cloned in vivo, using the mini-Mu replicon bacteriophage Mu dI5086 as the vector. A subclone containing a 7.8-kilobase (kb) EcoRI-HindIII fragment complemented all of our Gab- mutants. By restriction mapping, this DNA fragment was located at kb 2800.5 to 2808.5 on the physical map of the E. coli K-12 chromosome. A subclone containing a 1.8-kb EcoRI-SalI fragment complemented the gab-repressed strain CS101A (wild-type gabC) but did not complement any gab structural gene mutants. The gab genes are divergently transcribed from promoters located in the vicinity of the unique BamHI site. Transcription in both directions is under dual control of catabolite repression and nitrogen regulation. Using a procaryotic DNA-directed translation system, we observed three insert-coded polypeptide bands of 53 to 55, 45 to 48, and 40 to 43 kilodaltons (kDa). In vivo studies with subcloned fragments of the gab DNA identified the 53- to 55- and 45- to 48-kDa bands as products of the BamHI-SalI fragment and the 40- to 43-kDa band as the product of the EcoRI-SalI fragment. An additional 26- to 28-kDa band was identified as the product of the BamHI-HindIII fragment. Furthermore, the BamHI-SalI fragment was shown to specify synthesis of the two GABA enzymes, whereas synthesis of the GABA carrier was specified by the BamHI-HindIII fragment. No catalytic function in addition to its regulatory role could be attributed to the EcoRI-SalI gene product.
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PMID:In vivo cloning and characterization of the gabCTDP gene cluster of Escherichia coli K-12. 218 54

4-Aminobutyrate aminotransferase (EC 2.6.1.19, 4 aminobutyrate:2-oxoglutarate aminotransferase) is cleaved by trypsin, yielding an enzymatically active species which can be separated from the split peptides by gel filtration. The shortened enzyme derivative gives one band (Mr = 95,000) on polyacrylamide gradient gel electrophoresis. Changes in protein conformation induced by tryptic digestion were studied by fluorescence spectroscopy. The native enzyme tagged with the chromophore fluorescein yields a rotational relaxation time of 106 ns, whereas the trypsin-digested enzyme gives a rotational relaxation time of 33 ns. The decrease in rotational relaxation time is attributed to flexibility of the polypeptide chain with enhanced rotational freedom of the probe covalently linked to one thiol group. The reactivity of sulfhydryl groups toward 5,5'-dithiobis(2-nitrobenzoic acid) is also affected by trypsin cleavage. More--SH groups (2.6/dimer) become reactive toward 5,5'-dithiobis(2-nitrobenzoic acid) as a result of trypsin digestion. Local conformational fluctuations are induced as a result of tryptic cleavage, but the catalytic sites remain intact. The peptides released from 4-aminobutyrate aminotransferase were characterized by fingerprint analysis and their amino acid composition determined.
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PMID:Catalytic and structural properties of trypsin-treated 4-aminobutyrate aminotransferase. 661 42

Alanine-glyoxylate aminotransferase (AGT) 2 is a pyridoxal 5'-phosphate dependent, mitochondrial enzyme which, in the rat, is expressed at a high level in the kidney. The amino acid sequences of nine tryptic and seven CNBr peptides of the rat kidney AGT2 were determined. Three overlapping cDNAs encoding the AGT2 were cloned on the basis of its partial amino acid sequences by means of a polymerase chain reaction-based approach involving rat kidney poly(A)+ RNA. The complete cDNA sequence comprised 1,919 bases, and contained a 1,536-base open reading frame which encodes a polypeptide of 512 amino acid residues with a putative presequence consisting of 39 amino acid residues at the amino terminus, giving a precursor protein with a molecular mass of 57,150 Da. The sequence of AGT2 exhibits significant homology with neither peroxisomal AGT1 from human liver nor mitochondrial AGT1 from rat liver. However, the sequence of AGT2 exhibited 30.8, 29.2, and 27.1% identity with those of Escherichia coli 4-aminobutyrate aminotransferase, rat ornithine aminotransferase, and Pseudomonas cepacia 2,2-dialkylglycine decarboxylase, respectively. The active site sequences were also well conserved among these aminotransferases. AGT2, thus, is more similar to the other aminotransferases than to AGT1. The results suggest that the rat kidney AGT2 may play a biological role in amino acid metabolism distinct from that of AGT1.
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PMID:Molecular cloning and sequencing of a cDNA encoding alanine-glyoxylate aminotransferase 2 from rat kidney. 759 50