Bacterial NADH dehydrogenase and succinate dehydrogenase (NDH, SDH, SQR)

Bacterial NADH dehydrogenase (Complex I) and succinate dehydrogenase (Complex II) are two large, membrane-bound enzyme complexes central to the bacterial respiratory chain. NADH dehydrogenase catalyzes the transfer of electrons from NADH to ubiquinone, initiating the electron transport chain and supporting proton translocation across the membrane. Succinate dehydrogenase uniquely couples the oxidation of succinate to fumarate (a TCA cycle step) with direct electron transfer to ubiquinone, functioning as both a TCA cycle and electron transport chain enzyme. Both are multimeric complexes comprising several subunits (e.g., SDHA, SDHB, SDHC, SDHD for SDH), often containing prosthetic groups such as FAD and iron-sulfur clusters that facilitate electron transfer. These enzymes are highly conserved across taxa, but have species-specific subunit composition and regulation in bacteria. They are validated targets for antimicrobial drug development due to their essential role in maintaining bacterial energy metabolism and viability.

Other names

NADH oxidoreductaseComplex ISDHsuccinate-coenzyme Q reductase (SQR)respiratory complex IIsuccinate-coenzyme Q oxidoreductaseNADH:ubiquinone oxidoreductase

Inhibition of electron transport: Blocking electron flow through NADH dehydrogenase or succinate dehydrogenase, which collapses the proton motive force, disrupts ATP synthesis, and can induce cell death. Substrate analog inhibition: Competing with succinate or NADH for binding sites (competitive inhibition). Allosteric inhibition: Binding at regulatory sites affecting enzyme conformation and function.