Research Notes: Succinate Dehydrogenase

Succinate dehydrogenase (SDH) activity in the muscle biopsy report is significantly reduced to 31% of normal. SDH is the enzyme that catalyzes the succinate-to-fumarate reaction with formation of reduced flavin adenine dinucleotide (FADH₂) in the Kreb's cycle. Inhibition of FADH₂ production may inhibit the mitochondria electron transport chain at complex II, where FADH₂ is an electron donor. Notably, an anecdotal report of the use of L-carnitine fumarate for an infant with PWS has shown substantial benefit, even at a very low dose, which suggests the fumarate is entering the Kreb's cycle, perhaps thereby circumventing a substrate shortage.