A comparison of the kinetic properties of mouse brain glutamate decarboxylase activities in the mitochondrial and supernatant fractions

Several properties of the glutamate decarboxylase activities in the high-speed supernatant and water-washed mitochondrial fractions were compared. No significant differences in the values of Km for glutamate, the inhibitory effects of chloride ion, the proportion of pyridoxal-P independent activity remaining after exhaustive dialysis, the effects of added pyridoxal-P or the inhibitory effects of ATP were observed between the two fractions. The water-washed mitochondrial fraction was found to contain about 4 percent of the initial activity in the homogenate. Aside from the fact the small amount of glutamate decarboxylase found in the mitochondrial fraction cannot be released from the particles by washing or other mild treatments, there are presently no well documented differences between the glutamate decarboxylases found in the mitochrondrial and supernatant fractions.