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Adenosine triphosphate hydrolysis by purified rubisco activase
1United States Department of Agriculture, Agricultural Research Service Department of Agronomy, University of Illinois, Urbana 61801.
Archives of Biochemistry and Biophysics
|January 1, 1989
Summary
Rubisco activase, essential for activating ribulose bisphosphate carboxylase/oxygenase (rubisco), exhibits intrinsic ATPase activity. This activity, crucial for rubisco activation, is ATP-dependent and sensitive to ADP levels.
Area of Science:
- Biochemistry
- Plant Physiology
- Enzymology
Background:
- Ribulose bisphosphate carboxylase/oxygenase (rubisco) is a key enzyme in carbon fixation.
- Rubisco activase is a protein that facilitates the in vivo activation of rubisco.
Purpose of the Study:
- To investigate the biochemical properties of rubisco activase.
- To determine if ATPase activity is an intrinsic function of rubisco activase.
Main Methods:
- Purification of rubisco activase.
- Assay of ATPase activity using ATP-Mg.
- Determination of kinetic parameters (pH optimum, ATP concentration response).
- Assessment of inhibition by ADP and other molecules.
- Evaluation of heat lability and stability in the absence of ATP.
Main Results:
- Purified rubisco activase demonstrated specific ATPase activity (1.5 mumol min-1 mg-1 protein), hydrolyzing ATP to ADP and Pi.
- ATPase activity was optimal at pH 8.0-8.5, specific for ATP-Mg, and inhibited by ADP.
- Both ATPase and rubisco activation activities were heat labile and dependent on ATP concentration.
- Rubisco activation activity was influenced by both ATP and ADP concentrations.
Conclusions:
- ATPase activity is an intrinsic property of rubisco activase.
- The hydrolysis of ATP by rubisco activase is likely essential for its role in rubisco activation.
- Understanding these properties provides insight into the regulation of photosynthesis.