Figure 2. Overview of glutamine and glutamate metabolism in mammalian cells. Glutamate is produced from glutamine through glutaminase activity. Glutamate can then be converted to g-amino butyric acid (GABA), ornithine, 2-oxoglutarate, glucose or glutathione. The probable functions of the glutamate products are indicated as well as the cells or organs where the metabolic pathway preferentially occurs. NO, nitric oxide; iNOS, inducible nitric oxide synthase; glutamate Dh, glutamate dehydrogenase.