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Mitochondrial and cytosolic components of porphyrin/heme synthesis

In hepatorenal tyrosinemia, the cytosolic enzyme porphobilinogen synthase (ALA dehydratase, aminolevulinate dehydratase), top right of figure, is strongly inhibited by succinylacetone, producing an accumulation of δ-aminolevulinic acid (δ-ALA, dALA), which is excreted in the urine, and the development of porphyria-like neurologic crises. (Courtesy of Wikimedia Commons. Creative Commons Attribution-ShareAlike License.)