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(+) Enzyme activity is not stimulated by phosphate. Phosphate increases kcat, but decreases substrate affinity, resulting in unchanged enzyme activity. Homotetramer, dimer of dimers (By similarity). Does not assemble into higher oligomers (PubMed:23935106). Interacts with the PDZ domain of the syntrophin SNTA1. Interacts with the PDZ domain of TAX1BP3 (By similarity). Belongs to the glutaminase family. Extended N-terminus.