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)

4-Aminobutyrate-transaminase (4-aminobutyrate: 2-oxoglutarate amino-transferase, EC 2.6.1.19) from pig liver has been purified to electrophoretic homogeneity. It has a molecular weight of about 110 000 and is composed of two subunits of the same molecular weight but of different charges. Two forms of pig liver 4-aminobutyrate-transaminase were isolated by DEAE-cellulose chromatography and designated as 4-aminobutyrate-transaminase I and 4-aminobutyrate-transaminase II, corresponding to a cationic and anionic form. Some physical and kinetic properties of liver enzyme were compared to those of brain enzyme and no significant difference were found, except for their sedimentation coefficients and the charges of their subunits. The role of 4-aminobutyrate-transaminase in liver remains a matter of speculation, but could be related to a metabolic function.
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PMID:Purification and properties of 4-aminobutyrate 2-ketoglutarate aminotransferase from pig liver. 2 42

4-Aminobutyrate transaminase (GABA-T, 4-aminobutyrate alpha-oxoglutrate aminotransferase, EC 2.6.1.19) is an enzyme that inactivates the inhibitory neurotransmitter, GABA, but its pharmacological function is uncertain. Two forms of guiena pig brain GABA-T were isolated by DEAE-cellulose chromatography and designated as GABA-T-I and II, corresponding to an anionic and a cationic form. The enzymes were inhibited by high concentrations of a cationic form. The enzymes were inhibited by high concentrations of alpha-oxoglutrate (alpha-KG). Kinetic consists for GABA, when determined at pH 7.9 adn 1 mmol/l alpha-KG, were 0.74 mmol/l. GABA-T activity was inhibited by chloride and other anions. Kinetic analysis revealed chloride ion as a conpetitive inhibitor against GABA, but the Ki values differed among GABA-T-I and II (Ki equals 120 and 60 mmol/l, respectively). Similar degrees of difference were observed with acetate and lactate ion. These results suggest that GABA-T-II may regulate the GABA level in the inhibitory neurons and may play a similar functional role as that exhibited by monoamine oxidase in other synapses.
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PMID:Two forms of 4-aminobutyrate transaminase in guinea pig brain. 23 77

Highly purified 4-aminobutyrate aminotransferase from pig brain is susceptible to phosphorylation by the purified cAMP-dependent protein kinase catalytic subunit. Up to 0.7 moles of phosphate from ATP-(gamma)-32P can be incorporated per mole of dimeric holoenzyme. Maximum phosphorylation was observed within about 90 minutes at 30 degrees C. Despite the extensive degree of phosphorylation observed, no kinetic property of the enzyme was perceptibly altered. Removal of cofactor had no detectable impact on the extent of phosphorylation but thermal inactivation of the enzyme increased and mild reduction with sodium borohydride decreased the phosphorylatability of the aminotransferase. It was possible to separate the enzyme into phospho and dephospho forms by the use of DEAE chromatography. Validation that the two fractions represented genuine aminotransferase was obtained by proteolytic peptide mapping. The phospho form of the enzyme was found to possess little or no aminotransferase activity while that of the dephospho form exhibited higher specific activity than the purified enzyme prior to phosphorylation. Furthermore, the dephospho form of the enzyme could not be detectably phosphorylated by reincubation with the kinase following DEAE chromatography unless it was subjected to thermal inactivation. The stoichiometry of phosphorylation of the fraction containing 32P from DEAE chromatography was approximately 1 mole/mole of dimer. These results suggest that the substrate for phosphorylation by the kinase is a form of the aminotransferase which is somehow inactivated during routine purification even when extensive precautions are taken to maximally preserve catalytic activity.
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PMID:In vitro phosphorylation of 4-aminobutyrate aminotransferase by cAMP dependent protein kinase. 370 Jul 75