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

Glutamate decarboxylase, gamma-aminobutyrate-alpha-ketoglutarate aminotransferase and NAD-linked and NADP-linked succinic semialdehyde dehydrogenase, all constituting the GABA (gamma-aminobutyrate)-shunt pathway of glutamate metabolism are localized in the mitochondrial matrix in a streptomycin-bleached mutant of Euglena gracilis strain Z. Glutamate dehydrogenase, requiring NADP as the cofactor, was distributed in the cytoplasm. An improved version of the controlled digestion method for preparing Euglena mitochondria, which involves use of trypsin and a trypsin inhibitor and removal of broken cells before mechanical disruption of cells, is also described.
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PMID:Subcellular localization of the GABA-shunt enzymes in Euglena gracilis strain Z. 11 50

The chemical modification of pig liver 4-aminobutyrate aminotransferase by the antiepileptic drug 4-aminohex-5-enoate (Vigabatrin) has been studied. After inactivation by 14C-labeled Vigabatrin, the enzyme was digested with trypsin, and automated Edman degradation of the purified labeled peptide gave the sequence FWAHEHWGLDDPADVMTFSKK. Chymotryptic digestion of the tryptic peptide and sequencing of a resulting tripeptide identified the penultimate lysine residue of this peptide as the site of covalent modification. This lysine normally binds the coenzyme. Absorption spectroscopy demonstrated the absence of coenzyme from the tryptic peptide, and mass spectrometry showed its mass/charge ratio to be increased by 128. All of the bound coenzyme released after denaturation of the inactivated enzyme was as pyridoxamine phosphate. The structural nature of the modification is deduced, and mechanisms for its occurrence identified. Initially, 1 mol of radiolabeled inhibitor was bound per mol of monomer of the enzyme, although approximately half was released during denaturation and digestion, while the remainder was irreversibly bound. Coenzyme not released as pyridoxamine phosphate retained the absorbance characteristics of the aldimine, although the enzyme was completely inactive. Mass spectrometry of the sample of purified radiolabeled tryptic peptide revealed the presence of an approximately equal amount of a second fragment that contained no modification and from which the second lysine was absent, indicating that at the time of proteolysis the active site lysine was unaltered in 50% of the enzyme molecules.
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PMID:Chemistry of the inactivation of 4-aminobutyrate aminotransferase by the antiepileptic drug vigabatrin. 193 68

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