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Glutaminase (EC 3.5.1.2, glutaminase I, L-glutaminase, glutamine aminohydrolase) is an amidohydrolase enzyme that generates glutamate from glutamine. Glutaminase has tissue-specific isoenzymes. Glutaminase has an important role in glial cells. Glutaminase catalyzes the following reaction: Glutamine + H 2 O → glutamate + NH + 4
Catalyzing enzyme: glutaminase (EC 3.5.1.2) 2. Glutamate can be excreted or can be further metabolized to α-ketoglutarate. For the conversion of glutamate to α-ketoglutarate three different reactions are possible: Catalyzing enzymes: glutamate dehydrogenase (GlDH), EC 1.4.1.2
The ammonia produced in neurons is fixed into α-ketoglutarate by the glutamate-dehydrogenase reaction to form glutamate, then transaminated by alanine aminotransferase into lactate-derived pyruvate to form alanine, which is exported to astrocytes. In the astrocytes, this process is then reversed, and lactate is transported in the other direction.
The upper reaction shows how a transaminase combines with a glutamine residue, releasing ammonia, and then the combination reacts with the amine group of a lysine residue of another protein, setting the enzyme free again. Nine transglutaminases have been characterised in humans, [5] eight of which catalyse transamidation reactions.
In enzymology, a protein-glutamine glutaminase (EC 3.5.1.44) is an enzyme that catalyzes the chemical reaction. protein L-glutamine + H 2 O protein L-glutamate + NH 3. Thus, the two substrates of this enzyme are protein L-glutamine and H 2 O, whereas its two products are protein L-glutamate and NH 3.
Glutamine synthetase catalyzed reaction. Glutamine synthetase uses ammonia produced by nitrate reduction, amino acid degradation, and photorespiration. [4] The amide group of glutamate is a nitrogen source for the synthesis of glutamine pathway metabolites. [5] Other reactions may take place via GS.
In enzymology, a glutamine-pyruvate transaminase (EC 2.6.1.15) is an enzyme that catalyzes the chemical reaction. L-glutamine + pyruvate 2-oxoglutaramate + L-alanine. Thus, the two substrates of this enzyme are L-glutamine and pyruvate, whereas its two products are 2-oxoglutaramate and L-alanine.
In enzymology, a NAD + synthase (glutamine-hydrolysing) (EC 6.3.5.1) is an enzyme that catalyzes the chemical reaction. ATP + deamido-NAD + + L-glutamine + H 2 O AMP + diphosphate + NAD + + L-glutamate. In eukaryotes, this enzyme contains a glutaminase domain related to nitrilase. [1]