Glutamic decarboxylase, activity

Hotchkiss, A.J. Morgan, M.E. and Gibb, J.W. The long-term effects of multiple doses of methamphetamine on neostriatal tryptophan hydroxylase, tyrosine hydroxylase, choline acetyltransferase and glutamate decarboxylase activities. Life Sci 25 1373-1378. 1979. 

Kochhar et al. (1989) characterized an assay for glutamate decarboxylase activity. Glutamate and 4-aminobutyrate were separated on a Nucle-osil Q column. The mobile phase was 13 mAf trifluoroacetate and 1 mAf 1-octanesulfonate. Detection was by postcolumn derivatization with o-phthaldialdehyde reagent (1 mL/min) mixed with the column eluate (also 1 mL/min). The Teflon reaction coil (3 m x 0.3 mm) was kept at room temperature. The o-phthaldialdehyde reagent was prepared by dissolving 800 mg of o-phthaldialdehyde in 20 mL of ethanol plus 2.5 mL of 2-mercaptoethanol and mixing with 980 mL of 0.4 Af sodium borate (pH 9.7) and 3 mL Brij 35. The fluorometer was set to give excitation at 350 nm and emission was measured at 450 nm. 

Central effects on blood pressure regulation as a result of decreased synthesis of brain GABA and serotonin (5-hydroxytryptamine). Glutamate decarboxylase activity in the nervous system is especially sensitive to vitamin Bg depletion, possibly as a result of mechanism-dependent inactivation by transamination. Although there is no evidence that aromatic amino acid decarboxylase activity is reduced in vitamin Bg deficiency, there is reduced formation of serotonin in the central nervous system. 

Rick We did not change the production of GABA in the animals, but measured the differences that already existed between the strains. The ratio of radio carbon from U-[14C]glucose into GABA compared to that in glutamate is a measure of GABA synthesis and therefore, indirectly, of the optimal, rather than maximal, rate of glutamate decarboxylase activity for the strains. 

Phenyllactic and phenylpyruvic acids have an inhibitory effect on dopa decarboxylase and glutamic decarboxylase activity, but phenylalanine does not. Phenyl-acetic acid in equimolar concentrations had only half the inhibitory power of the two other metabolites. These findings might explain why low-phenylalanine diets restore pigmentation to normal in phenylke-tonuric individuals. 

Plants can use urea and a variety of relatively simple amines as a source of nitrogen. The first step in the metabolism of amines is probably oxidation to the corresponding aldehyde and ammonia (see section V.A). The amines occurring naturally in plants include methylamine, isoamylamine and other volatile amines, which are found in some flowering species. The route to these amines is not thought to involve decarboxylation of amino acids, but little is yet known with certainty about the metabolism of amines in plants. Glutamic decarboxylase activity has been detected in a wide variety of higher plants, consistent with the widespread distribution of the product of decarboxylation, y-aminobutyric acid. 

Hsu, CC, Thomas, C, Chen, W, Davis, KM, Foos, T, Chen, JL, Wu, E, Floor, E, Schloss, JV and Wu, JY (1999) Role of synaptic vesicle proton gradient and protein phosphorylation on ATP-mediated activation of membrane-associated brain glutamate decarboxylase. J. Biol. Chem. 274 24366-24371. 

Pyridoxine dependency. Pyridoxine dependency is characterized by severe seizure activity of early onset, perhaps even in utero. Patients respond dramatically to parenteral administration of pyridoxine (10-100 mg). Speculation has centered on the possibility that the disease involves faulty binding of pyridoxine, a cofactor in the glutamate decarboxylase reaction, to the enzyme protein. 

Peat, M. A., and Gibb, J. W. (1983) The effects of phencyclidine on glutamic acid decarboxylase activity in several regions of the rat brain. Neurosci. Lett., 35 301-306. 

Increased glutamic acid decarboxylase activity Vasoactive PAF inhibition... 

Dye, D.J., and Taberner, P.V. The effects of some newer anaesthetics on the in vitro activity of glutamate decarboxylase and GABA transminase in crude brain extracts and on the levels of amino acids in vivo. J. Neurochem. 24 997-1001, 1975. 

Beta-chloroalanine and serine O-sulfate can undergo (3 elimination (as in Eq. 14-29) in active sites of glutamate decarboxylase or aspartate aminotransferase. The enzymes then form free aminoacrylate, a reactive molecule that can undergo an aldol-type condensation with the external aldimine to give the following product.1... 

The ratio of transamination decarboxylation is relatively small - of the order of 1 10,000 for glutamate decarboxylase. Nevertheless, this is sufficient to result in significant loss of active enzyme, andMeister (1990) suggested that this may be a control mechanism rather than simply a lack of reaction specificity. 

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