{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Succinate dehydrogenase (SDH) is a heterotetrameric protein complex found in the inner mitochondrial membrane of eukaryotic cells and part of the tricarboxylic acid (TCA) cycle and electron transport chain. The 4 subunits of SDH are SDHA (flavoprotein), SDHB (contains 3 iron-sulfur clusters), SDHC and SDHD (two membrane-bound proteins anchored to the inner mitochondrial membrane). SDH catalyzes the oxidation of succinate to fumarate and the concomitant reduction of ubiquinone to ubiquinol. Mutations in SDH subunits are associated with a variety of disease phenotypes that can be grouped into two categories: cancer and neurodegeneration. Mutations in the core subunits are most commonly associated with paraganglioma, pheochromocytoma, renal cell carcinoma, and wild-type gastrointestinal stromal tumors. SDH activity also supports normal neurologic development, and functional mutations in SDH have been observed in Leigh syndrome, infantile leukodystrophy, and progressive encephalomyopathy."}]}]}