Reduction of nuclear encoded enzymes of mitochondrial energy metabolism in cells devoid of mitochondrial DNA

► We examined OXPHOS and citrate synthase enzyme activities in HEK293 cells devoid of mtDNA. ► Enzymes partially encoded by mtDNA show reduced activities. ► Also the entirely nuclear encoded complex II and citrate synthase exhibit reduced activities. ► Loss of mtDNA induces a feedback mechanism that downregulates complex II and citrate synthase.