Purification and characterization of uroporphyrinogen decarboxylase from tobacco leaves

摘要

1. Uroporphyrinogen decarboxylase which catalyzes the formation of coproporphyrinogen from uroporphyrinogen is located in the soluble fraction of tobacco leaves and was purified 72 fold through ammonium sulphate precipitation and calcium phosphosphate gel absorption. 2. Kinetic studies indicated that the apparent Michaelis constant was 1×10-6M for uroporphyrinogen III (pH 6.5; 37°C). Uroporphyrinogen III served as a much better substrate than uroporphyrinogen I under the standard conditions of this study. 3. Enzyme activity was inhibited by thiol reagents and heavy divalent cations and was stimulated by some chelating agents. 4. Both chloride and fluoride salts inhibited the formation of coproporphyrinogen from uroporphyrinoge