Catalyzes the first reaction in the primary pathway for the renal catabolism of glutamine. Plays a role in maintaining acid-base homeostasis. Regulates the levels of the neurotransmitter glutamate, the main excitatory neurotransmitter in the brain. H2O + L-glutamine = L-glutamate + NH4(+) Enzyme activity is increased by phosphate, due to increased kcat and increased substrate affinity. Homotetramer, dimer of dimers. Tetramer composed of 68 and 65 kDa peptides in a 1:3 ratio. Can assemble into higher oligomers (in vitro), but the physiological significance of this is not clear (PubMed:23935106). Interacts with RAF1 and MAP2K2 (By similarity). Interacts with ATCAY; the interaction is direct and may control GLS localization, negatively regulating its activity. The 74-kDa cytosolic precursor is translocated into the mitochondria and processed via a 72-kDa intermediate to yield the mature 68 and 65-kDa subunits. Produced by the proteolytic processing of the 74-kDa cytosolic precursor. Produced by the proteolytic processing of the 74-kDa cytosolic precursor. Kidney, brain, and intestine. The C-terminal ANK repeats prevent the assembly of the supra-tetrameric filaments. A highly mobile activation loop at the dimer-dimer interface is important for enzyme activity. Synthesized as a 74-kDa cytosolic precursor which is proteolytically processed by the mitochondrial-processing peptidase (MPP) via a 72-kDa intermediate to yield the mature mitochondrial 68- and 65-kDa subunits. Belongs to the glutaminase family.