Preparation & some properties of soluble succinic dehydrogenase from higher plants

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Abstract
Succinic dehydrogenase was obtained in a soluble form from bean roots (Phaseolus vulgaris) and tobacco leaves (Nicotiana tabacum) by extracting an acetone powder of mitochondria with dilute buffer. The enzyme was partially purified and some of its properties studied. Succinic dehydrogenase from these plants exhibited a rather sharp pH optimum at approximately pH 7.4. The KM of the enzyme for succinate was 1 x 10-3 [image] at 30[degree]C and pH 7.4. Malonate competitively inhibited succinic dehydrogenase and the Ki for malonate was 2.4 x 10-4 [image] at 30[degree]C and pH 7.4. Enzyme activity was reduced 75% by 1 x 10-5 [image] p-hydroxymercuribenzoate. The enzyme from bean roots and tobacco leaves was activated by succinate, but phosphate did not stimulate activity. Tris buffer retarded succinate activation of succinic dehydrogenase. Enzyme extracts from bean roots and tobacco leaves exhibited similar properties.