PPM1K and neoplasm: After the intake by tumor cells, branched-chain amino acid transaminase 1 and 2 (BCAT1/2) transfers nitrogen of BCAAs to α-ketoglutarate (αKG) to produce glutamine and branched-chain keto acid (BCKA), which is then metabolized by branched-chain alpha-keto acid dehydrogenase complex (BCKDH) and some other enzymes to produce tricarboxylic acid (TCA) cycle intermediates acetyl-CoA and/or succinyl-CoA, thus fueling tumor cell proliferation and providing some building bricks to biogenesis253 (Fig. 6).