Glutaminase is an amidohydrolase enzyme that generates glutamate from glutamine. Glutamate production by mitochondrial glutaminase is a key process for body homeostasis, and a crucial carbon donor for amino acid and lipid synthesis in tumor cells.

Glutaminase has tissue-specific isoenzymes. Three mammalian glutaminases have been identified: the liver-type [LGA or GLS2], the kidney-type [KGA] and Glutaminase C [GAC] a splice variant of KGA (both usually referred to as GLS1). GLS1 is a therapeutic target for cancer. GLS1 catalyzes the hydrolysis of glutamine to glutamate, which is used in the citric acid cycle (TCA) of cancer cells undergoing an aberrant glycolytic flux as a non-glucose-derived source for anaplerosis. GAC plays an essential role in the transformation of NIH 3T3 fibroblasts by Rho GTPases, as well as in the proliferative and invasive activities of various cancer cells.