Inhibition by hemin of in vitro translocation of chicken liver delta-aminolevulinate synthase into mitochondria.

The precursor form of chicken liver delta-aminolevulinate synthase was synthesized in a reticulocyte lysate cell-free translation system and then incubated with the homologous liver mitochondria. The precursor enzyme was incorporated into the mitochondria with an attendant processing to the mature enzyme. In this in vitro experimental system, both the transport and processing of the enzyme were significantly inhibited by the addition of hemin as low as about 3 microM. This provides further support to the view, which had been derived from the studies in vivo, that inhibition by hemin of the translocation of delta-aminolevulinate synthase into mitochondria could be one of the regulatory mechanisms for heme biosynthesis in the liver cells.