Table I.

Comparison of Rubisco activation and ATPase activities of recombinant Arabidopsis Rubisco activase

Enzyme	Rubisco Activation		ATPase Activity		Rubisco Activation: ATPase
	Activitya	RWT	Activityb	RWT	Ratio	RWT
		%		%		%
43-kD RWT	4.2	–	0.55	–	7.8	–
Q111D	8.2	190	0.78	140	10.6	140
Q111E	10.0	240	0.68	120	14.7	190
Q111S	2.3	55	0.35	64	6.5	83

Rubisco activation was determined by following phosphoglyceric acid production in a coupled spectrophotometric assay. ATPase activity in the absence of ADP was measured by a spectrophotometric assay modified from Robinson and Portis (1989). Rates represent steady-state values averaged over a 2-min time span. The Rubisco activation to ATPase ratio is a measure of the coupling efficiency. The results are the average of duplicate assays.

^a Units of activity are μmol CO₂ min⁻¹ mg⁻¹ Rubisco min⁻¹ mg⁻¹ protein. 

^b Units of activity are μmol ADP min⁻¹ mg protein⁻¹.