1-1-1. Succinate dehydrogenase (SDH) and fumaratehydratase (FH); SDH is involved in the TCA cycle, catalyzesthe conversion from succinate to fumarate, and releasesone molecular-reduced flavin adenine dinucleotide. SDHmutations are commonly found in paraganglioma, gastricstromal tumors, and childhood T-cell acute leukemia (22,23).Germline mutations in SDH seem to be closely associatedwith human head and neck paragangliomas (23). Thesefacts suggest that SDH mutations may provide a growthadvantage in the initial stages of tumorigenesis. FH, anenzyme similar to SDH, also catalyzes the reaction fromAltered Energy Metabolism in Cancer