J.C. Servaites, in Plant Physiol. (1985) 78:839-843, observed that rubisco extra

Question

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.

Explanation / Answer

one of the possible reasons could be Rubisco inhibitor having a strong binding with the enzyme.

It is because of its strong binding it withstood extensive dialysis, gel filtration, or heat treatment as such methods didin't break the association and the enzyme-inhibitor complex remained intact after treatment. However, in case of ammonium chloride precipitation it could be that the inhibitor and enzyme precipitates at different concentrations of ammonium chloride and hence were seperated hence restoring the specific activity of enzyme.

Hope it helps ... feel free to discuss ... I will be glad to help you ,.... Regards

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