Measurement of the Enzyme-CO2-Mg2+ Form of Spinach Ribulose 1,5-Bisphosphate Carboxylase/Oxygenase

Abstract
When the amount of activation of ribulose 1,5-bisphosphate carboxylase has been measured, two forms of the enzyme, not one, are actually determined experimentally. Only the enzyme-activator, CO2-Mg2+ form can bind ribulose bisphosphate for reaction with substrate CO2 or O2. A method is presented which measures only this catalytically active form by stabilizing it with ribulose biphosphate just before dilution and assay in Mg2+-free reaction medium.