Evaluation of Fe(III) reduction by mitochondria induced with a respiratory substrate NADH or succinate,using a Fe(II)-specific chelator bathophenanthroline disulfonate in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

Mitochondria are the centers of the cellular iron metabolism. Iron utilization by mitochondria is deeply related to their respiratory chain activity. We isolated mitochondria from Saccharomyces cerevisiae and examined Fe(III) reduction induced by a respiratory substrate (NADH or succinate), using a Fe(II)-specific chelator (bathophenanthroline disulfonate). In the presence of either 50 μM NADH or 5 mM succinate, the amount of reduced Fe(III) was linearly correlated with the amount of mitochondria. As the concentration of the substrate increased, the rate of the mitochondrial Fe(III) reduction reached a plateau. In the presence of 1 mM ADP or 1 mM ATP, the extramitochondrial Fe(III) reduction was repressed when succinate was used as the substrate, but not when NADH was used. ADP had an inhibitory effect even under low concentration of succinate, suggesting that ADP and ATP acted in a manner of both competitive and uncompetitive inhibition.