Parry, M.A.J. Godfrey Schmidt, C.N. Cornelius, M.J. Keys, A.J. Millard, B.N. Gutteridge, S. text xx 9999 monographic und

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Ribulose bisphosphate carboxylase/oxygenase (E.C. 4.1.1.39)from wheat (Triticum aestivum L.), already activated by reaction with CO2 and Mg2+, was increased in activity on addition of inorganic orthophosphate. This further activation took place without a significant increase in the amount of bound activating CO2 and the effect was relatively greater with smaller amounts of bound CO2. With less than 2-0 mol of CO2 bound per mol holoenzyme, phosphate increased activity about five-fold whilst with 70 mol of bound activating CO2 per mol holoenzyme, phosphate increased activity by a factor of only 1 -8. This decrease in the effect of orthophosphate with increase in bound activating CO2 suggests negative co-operativity between activated sites. The stimulation of activity by inorganic orthophosphate must be a process distinct from activation by CO2; it was observed with both the slow and the rapidly activating forms of ribulose bisphosphate carboxylase/oxygenase from wheat. RIBULOSE BISPHOSPHATE CARBOXYLASE ACTIVATION INORGANIC ORTHOPHOSPHATE CO2 CO-OPERATIVITY https://drive.google.com/file/d/1i_HuWPZYLc2SPAu0tU6YRNj9Bn3jKZav/view?usp=drivesdk https://drive.google.com/file/d/1i_HuWPZYLc2SPAu0tU6YRNj9Bn3jKZav/view?usp=drivesdk 250602 20260521091450.0