Exogenous quinones directly inhibit the respiratory NADH dehydrogenase in Escherichia coli.
The ability of naphthoquinones to generate reactive oxygen species has been widely exploited in studies of oxidative stress. However, excess superoxide dismutase and catalase failed to protect Escherichia coli in rich medium against growth inhibition by plumbagin, indicating that its toxic effect was not due to the production of partially reduced oxygen species. Respiration failed immediately upon the addition of growth-inhibitory levels of plumbagin. Studies in vitro showed that plumbagin and other redox-active quinones intercept electrons from NADH dehydrogenase, the primary respiratory dehydrogenase in glucose-containing media. An excess of oxidative substrate, such as plumbagin, inactivates this enzyme, which appears to be redox-regulated. The resultant respiratory arrest is a cautionary example of metabolic dysfunction from redox-cycling drugs that cannot be attributed to superoxide or hydrogen peroxide.
Imlay
J
J
Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710.
Fridovich
I
I
D002462:Cell Membrane / Q000201:enzymology; D003574:Cytochrome c Group / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D006861:Hydrogen Peroxide / Q000378:metabolism; D007700:Kinetics; D009245:NADH Dehydrogenase / Q000037:antagonists & inhibitors*; D009285:Naphthoquinones / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000187:drug effects; D011809:Quinones / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism
D003574:Cytochrome c Group; D009285:Naphthoquinones; D011809:Quinones; D013481:Superoxides; D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase; D009245:NADH Dehydrogenase; C014758:plumbagin