Heme Synthesis in Soybean Root Nodules

Abstract
During nodulation of soybean (Glycine max) by Rhizobium japonicum, variations in the activities of two enzymes of heme biosynthesis, δ-aminolevulinic acid synthase (ALAS) and δ-aminolevulinic acid dehydrase (ALAD) are described. δ-Aminolevulinic acid synthase activity is found in the bacteroid fraction of nodules, but is not detected in the plant fraction. Bacteroid ALAS activity parallels heme accumulation during nodule development. δ-Aminolevulinic acid dehydrase activity is found in both bacteroid and plant cytosol fractions. Bacteroid ALAD activity is constant or increases during nodulation while plant ALAD activity falls.
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