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The end product of the glutaminase reaction, glutamate, is a strong inhibitor of the reaction. Changes in glutamate dehydrogenase, which converts glutamate to 2-oxoglutarate and thereby decreases intramitochondrial glutamate levels, are thereby an important regulatory mechanism of glutaminase activity.
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
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 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]
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.
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.
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.
In enzymology, a glutamin-(asparagin-)ase (EC 3.5.1.38) is an enzyme that catalyzes the chemical reaction L-glutamine + H 2 O ⇌ {\displaystyle \rightleftharpoons } L-glutamate + NH 3 Thus, the two substrates of this enzyme are L-glutamine and H 2 O , whereas its two products are L-glutamate and NH 3 .