Effect of ligandin on the efflux of Co-deuteroporphyrin from isolated rat liver mitochondria

Abstract

Summary Ligandin markedly accelerated the efflux of Co-deuteroporphyrin from tightly coupled mitochondria. This was associated with an increase in the rate of Co-deuteroporphyrin synthesis. The addition of 0.1 M KCl to the medium reduced but did not abolish the effect on efflux. In the absence of Co 2+ , ligandin inhibited deuteroporphyrin uptake by mitochondria. When added to sonicated mitochondria ligandin inhibited Co-deuteroporphyrin synthesis. These results suggest that ligandin plays an important part in the transfer of heme from mitochondria to its other sites of utilization. The effect of ligandin on heme release requires intact functional mitochondrial membranes and overcomes the tendency to deplete the porphyrin substrate for which it has affinity.