Paraganglioma (PGL) is a rare tumor that may be found in the abdomen, the thorax, or the head and neck region. Succinate dehydrogenase (SDH, or succinate-coenzyme Q reductase) was recognized as one of the key molecules playing a role in the pathogenesis of the tumor.
An enzyme complex bound to the inner mitochondrial membrane, SDH is the only enzyme that participates in both the citric acid cycle and the mitochondrial electron transport chain. It is a heterotetramer divided into three domains: SDHA, the catalytic domain, SDHB, the electron transfer subunit; and SDHC and SDHD, the anchor subunits.