Purification and Regulation of Phosphate-Activated Pig Brain Glutaminase
Glutaminase (EC 188.8.131.52 L-glutamine amidohydrolase) catalyses the hydrolysis of L-glutamine to glutamate and ammonia. As this reaction is practically irreversible, glutaminase is likely to be a key enzyme which, directly or indirectly, regulates the level of glutamate, an excitatory transmitter candidate in the brain. Moreover, glutamate is the substrate for the decarboxylase reaction which leads to the formation of GABA, an inhibitory transmitter candidate. However, the contribution by glutaminase to the synthesis of these essential metabolites, glutamate and GABA, is poorly understood. Other aspects of the glutaminase reaction should also be mentioned. Since the amide group of glutamine is a major contributor to the pool of labile amide groups (Weil-Malherbe and Gordon, 1971), glutaminase may be a major regulator of this pool, thus making ammonium ions available for various synthetic reactions, e.g. the important synthesis of amino acids and proteins from carbohydrates in the brain. For these reasons, knowledge of the regulation of glutaminase will probably be required for the proper understanding of the essential metabolic reactions in the brain.
KeywordsPotassium Phosphate Sodium Dodecyl Sulphate Citric Acid Cycle Negative Cooperativity Essential Metabolite
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