Abnormal muscle tissue enzyme activity or level Abnormal muscle succinate dehydrogenase staining 2023-06-12T13:36:22Z Succinate dehydrogenase (SDH) is a mitochondrial enzyme complex located in the inner mitochondrial membrane that has dual roles in the oxidation of succinate to fumarate in the Krebs cycle and in electron transport during oxidative phosphorylation. Any deviation from the normal amount of staining of succinate dehydrogenase in skeletal muscle tissue.