Properties of L-glutamate decarboxylase from brains of adult and newborn mice

Wu, J.Y.; Wong, E.; Saito, K.; Roberts, E.; Schousboe, A.

Journal of Neurochemistry 27(3): 653-659


ISSN/ISBN: 0022-3042
PMID: 9480
DOI: 10.1111/j.1471-4159.1976.tb10390.x
Accession: 068517861

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L-Glutamate 1-carboxy-lyase (EC (GAD) and 4-aminobutyrate-2-oxo-glutarate aminotransferase (EC (GABA-T) have been purified from mouse brain and their properties extensively studied. The above enzymes were prepared from a water lysate of crude mitochondrial fraction, which accounted for only 25-30% of total GAD or GABA-T activities in brain. A procedure was developed which liberated approximately 85% of total GAD and GABA-T activities into supernatant. Two distinct, well-separated peaks with GAD activity and a single peak with GABA-T activity were observed when a concentrated extract from brain of adult or newborn mice was chromatographed on Sephadex G-200 or Bio-Gel A-1.5 m. The 1st peak appeared in the void volume and was therefore, an entity of high MW. The 2nd peak gave elution characteristics which were identical to those of the enzyme purified previously (MW = 85,000). These 2 GAD peaks were also clearly separated on polyacrylamide gel electrophoresis. The GAD activities in the 2 peaks showed similar pH profiles (optimum, 6.5), Km values (1-2 mM), immunodiffusion patterns and inhibitions by anti-GAD IgG [immunoglogulin G] prepared against GAD purified from synaptosome-containing crude mitochondrial fractions (60-80%). The physiological implications of high and low MW forms of GAD were discussed.