The control of heme synthesis in soybean root nodules

1. 1. Heme synthesis from δ-amino[4- 14 C]levulinic acid in soybean root nodule extracts is inhibited by exogenous heme with maximum (50%) inhibition occurring at a heme concentration of 1 · 10 −4 M. Removal of the exogenous heme results in a reversal of this inhibition. 2. In the nodule extracts, heme synthesis from δ-amino[su14C]levulinic acid is stimulated by the addition of apo-leghemoglobin. We conclude that heme biosynthesis in soybean root nodules is endproduct, negatively feedback controlled, and we suggest that heme synthesis in this symbiotic complex may be coupled to that of apo-leghemoglobin.