GLS and glioblastoma: The first step of glutaminolysis is the deamidation ofglutamine to glutamate via the enzyme glutaminase (GLS), and then the conversion ofglutamate to α-ketoglutarate (α-KG) via glutamate dehydrogenase.Glutamine-derived α-KG is a TCA intermediate and the major source of OAA,which replenishes the exported citrate for fatty acid synthesis, in some tumor cells.For example, 13C labeled NMR spectroscopy in human GBM cells demonstrate glutamine tocontribute to the bulk of anaplerotic carbon to the TCA cycle [15,28].