Several amino acid-degrading enzymes, including arginine deiminase, L-methionase, L-arginase, lysine oxidase, L-glutaminase, and L-phenylalanine, are currently under clinical evaluation, while L-asparaginase has been approved as an effective therapy against acute lymphoblastic leukemia (ALL) and other auxotrophic malignancies [159]. This evidence concerns the gene GLS2 and acute lymphoblastic leukemia.