Figure 3.

Schematic illustration of the relationship between heme synthesis and the IDH1 mutation. Thick arrows indicate metabolism activation, white arrows the activated enzymes or plasma membrane structures involved in porphyrin metabolism. ABCG2 transports porphyrins from the cytoplasm to the extracellular space. NADP⁺ levels increase during metabolization to bilirubin by heme. The IDH1 mutation may promote a defense system against ROS by activating catalase, HO-1, etc. The intracellular PPIX level is downregulated. (ABCG2 = ATP-binding cassette transporter G2; CO = carbon monoxide; FECH = ferrochelatase; HO-1 = heme oxygenase-1; PP = protoporphyrin; ROS = reactive oxygen species).