JC Servaites in Plant Physiol 1985 78839843 observed that ru

J.C. Servaites, in Plant Physiol. (1985) 78:839-843, observed that rubisco extracted from tobacco leaves collected before dawn had a much lower specific activity than the enzyme extracted from leaves collected at noon. This difference persisted despite extensive dialysis, gel filtration, or heat treatment of the predawn enzyme extract. However, precipitation of the predawn enzyme by 50% (NH₄)₂SO₄ restored the specific activity to the level of noon-collected enzyme.

Explain what each of these procedures (dialysis, gel filtration, heat treatment) would do to the enzyme extract and suggest an explanation for why the ammonium sulfate precipitation restored the specific activity and none of the other treatments were effective.

Solution

The procedures of dialysis which is basically based on their differing ability of particles to pass through a membrane in a liquid, as precipitation of the predawn enzyme by 50% (NH4)2SO4 restored the specific activity to the level of noon-collected enzyme. It is not gel filtration as this process is a usually applied to macromolecules.