A hematologist’s narrow view of glutamine and glutamate metabolism. Glutamine is transported across the erythrocyte membrane, where it can support the synthesis of NAD(H), NADP(H), GSH, and glutamate. However, these can also be synthesized in pathways that do not require glutamine as a proximal precursor. For example, the majority of erythrocyte glutamate appears to derive from alanine via ALT.¹⁰  NAD(P) also derives from nicotinamide mononucleotide. NADP(H) and GSH are used by the erythrocyte to counter oxidative injury. Several intermediate steps are omitted for clarity. αKG, α-ketoglutarate; ALT, alanine aminotransferase; AST, aspartate aminotransferase; GA, glutamine aminohydrolase; NAAD, nicotinic acid adenine dinucleotide; NAD(H), reduced nicotinamide adenine dinucleotide; NADP(H), reduced nicotinamide adenine dinucleotide phosphate; NADS, nicotinamide adenine dinucleotide synthase; NMN, nicotinamide mononucleotide.