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(+) Isoform 1 and isoform 2 are activated by phosphate, due to increased affinity for glutamine (PubMed:22228304, PubMed:23935106, PubMed:27542409). At phosphate concentrations above 10 mM, isoform 2 is more efficient than isoform 1. Homotetramer, dimer of dimers (PubMed:22228304, PubMed:27542409). The tetramers can assemble into rod-like 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 (PubMed:16899818). 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. A highly mobile activation loop at the dimer-dimer interface is important for enzyme activity. The C-terminal ANK repeats prevent the assembly of the supra-tetrameric filaments. 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. Death during the first days after birth. Pups appear normal and display normal levels of activity, but their activity is disorganized. Pups do not orient to the dam, do not succeed in grasping a nipple and do not feed properly. In addition, they display altered respiration. Belongs to the glutaminase family. Extended N-terminus.