Purification and properties of {delta}-aminolevulinic acid dehydratase from radish cotyledons

-Aminolevulinic acid dehydratase (5-aminolevulinate hydro-lyase,EC 4.2.1.24 EC] ) was purified from greening radish cotyledons. Thefinal product was homogeneous on polyacrylamide disc gel electrophoresisand had a molecular weight, estimated by gel filtration, of282,000 daltons. The enzyme seems to require magnesium ion aswell as sulfhydryl compounds for maximum activity. EDTA anda low concentration of zinc ion markedly inhibited the activity.The optimum pH was 8.0; the Km value for -aminolevulinic acidwas 3.85?10^–4M. Levulinic acid was a competitive inhibitorof the enzyme, with a Ki of 2.14?10^–4M. These propertieswere compared with those of microorganism and animal -aminolevulinicacid dehydratases. (Received November 22, 1976; )