Fluorescence-Guided Resection of Malignant Glioma with 5-ALA

Figure 1

The simplified synthetic pathway of ALA-induced PpIX. ALA is an endogenous substance. It is incorporated into the mitochondria, repeatedly transported between the cytoplasm and the mitochondria, and finally used for heme synthesis. ALA is converted into porphobilinogen by the enzyme ALA dehydratase, and porphobilinogen is sequentially converted into hydroxymethylbilane, uroporphyrinogen III, coproporphyrinogen III, protoporphyrinogen IX, and finally PpIX by the enzyme protoporphyrinogen oxidase. The final product heme is synthesized from PpIX and iron (Fe) by the enzyme ferrochelatase (FeC). This biosynthetic pathway is considered to be the same in all organisms (PENTA: pentacarboxyl porphyrin, COPRO I or III: coproporphyrin I or III, and HARDERO: harderoporphyrin).