Rubisco Activase Mediates ATP-Dependent Activation of Ribulose Bisphosphate Carboxylase

The activation level of ribulosebisphosphate carboxylase following preincubation with ribulose 1,5-bisphosphate was increased by ATP and ribulosebisphosphate carboxylase activase in the absence of thylakoids or illumination. Maximal activation was obtained with 0.5 millimolar ATP in the presence of an ATP regenerating system (phosphoenolpyruvate and pyruvate kinase). Without the ATP regenerating system, activation was lower, linearly dependent on ATP concentration up to 1.0 millimolar, and was strongly inhibited by ADP.