Adenosine triphosphate hydrolysis by purified rubisco activase

• Published in: Archives of biochemistry and biophysics Vol. 268; no. 1; pp. 93 - 99
• Main Authors: Robinson, Simon P., Portis, Archie R.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 1989; Elsevier
• Subjects: Adenosine Triphosphate - metabolism; Analytical, structural and metabolic biochemistry; ATP; Biological and medical sciences; Cations, Divalent; Enzyme Activation; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Hydrolysis; Kinetics; Lyases; Plant Proteins; Ribulose-Bisphosphate Carboxylase - metabolism; ribulose-bisphosphate carboxylase activase; Substrate Specificity; Vegetals; Ribulosebisphosphate carboxylase; Enzymatic activity; Radiolabelling; Enzyme; ATPase; ATP; Ultraviolet visible spectrometry
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1016/0003-9861(89)90568-7

Activation of ribulose bisphosphate carboxylase/oxygenase (rubisco) in vivo is mediated by a specific protein, rubisco activase. In vitro, activation of rubisco by rubisco activase is dependent on ATP and is inhibited by ADP. Purified rubisco activase hydrolyzed ATP with a specific activity of 1.5 μmol min −1 mg −1 protein, releasing approximately stoichiometric amounts of ADP and P i. Hydrolysis was highly specific for ATP-Mg and had a broad pH optimum, with maximum activity at pH 8.0–8.5. ATPase activity was inhibited by ADP but not by molybdate, vanadate, azide, nitrate, or fluoride. Addition of rubisco in either the inactive or activated form had no significant effect on ATPase activity. Incubation of rubisco activase in the absence of ATP resulted in loss of both ATPase and rubisco activation activities. Both activities were also heat labile, with 50% loss in activity after 5 min at 38 °C and complete inhibition following treatment at 43 °C. Both activities showed a sigmoidal response to ATP concentration, with half-maximal activity at 0.053 m m ATP. Rubisco activation activity was dependent on the concentrations of both ATP and ADP. The results suggest that ATPase activity is an intrinsic property of rubisco activase.