Electrons sidetracked from redox reactions are responsible for the formation of reactive oxygen species (ROS) in organisms. One known intervention that can diminish ROS generation in Saccharomyces cerevisiae, decreasing electron leakage in mitochondria, is calorie restriction (CR). Here we show that deltaLPD1 S. cerevisiae, a strain that does not display dihydrolipoil dehydrogenase activity in pyruvate and alpha-ketoglutarate dehydrogenase complexes, does not exhibit beneficial phenotypes of CR in the late sationary phase such as improved O₂ consumption and decreased ROS formation. In order to investigate if tricarboxylic acid cycle integrity, and not specifically alpha-ketoglutarate dehydrogenase, is necessary for the occurence of long-term CR beneficial effects, we measured O₂ consumption and H₂O₂ production in deltaMDH1 cells, a strain that does not express mitocondrial malate dehydrogenase isoform. Surprinsingly, deltaMDH1 S. cerevisiae bevaved similarly to WT. Interestingly, the deletion of lpd1 in strains that exhibit relevant chronic oxidative stress, such as deltaNPT1 and deltaBNA6 - in which intracellular NAD⁺ content is lower than WT - is capable of preventing excessive electron leakage observed in these strains. Altogether, our results indicate that lpd1, but not mdh1, is necessary for long-term beneficial effects of CR in S. cerevisiae and that pyruvate and alpha-ketoglutarate dehydrogenases are important sites of electron leakage in strains with decreased NAD⁺ content. We have thus identified dihydrolipoil dehydrogenase as a novel source of electron leakage and ROS formation in S. cerevisiae. Supported by CNPq and FAPESP.