Plays an important role in the regulation of glutamine catabolism. Promotes mitochondrial respiration and increases ATP generation in cells by catalyzing the synthesis of glutamate and alpha-ketoglutarate. Increases cellular anti-oxidant function via NADH and glutathione production. May play a role in preventing tumor proliferation. H2O + L-glutamine = L-glutamate + NH4(+) Homotetramer, dimer of dimers (Probable). Does not assemble into higher oligomers (By similarity). Interacts with the PDZ domain of the syntrophin SNTA1. Interacts with the PDZ domain of TAX1BP3 (PubMed:11163757). Highly expressed in liver. Expressed in brain and pancreas. Not observed in heart, placenta, lung, skeletal muscle and kidney. Expression is significantly reduced in hepatocellular carcinomas. Up-regulated by P53 (at protein and mRNA level) under both stressed and non-stressed conditions. Belongs to the glutaminase family.