RuBP carboxylase determination by enzymic estimation of D-3-PGA formed.
RuBPcarboxylase activity was measured in extracts of barley (Hordeum Vulgare L., cv. HOP) seedlings both with the standard radiometric method and by measuring D-3-phosphoglyceric acid formed enzymically in a two stage assay. In the different conditions used, characterized by different NaHCO3 concentrations, different pH and the presence and absence of oxygen, essentially the same ratio of D-3-PGA formed per (14)CO2 fixed was obtained. This ratio respected the known stoichiometry of two molecules of D-3-PGA formed per CO2 fixed.It is suggested that measurement of D-3-PGA enzymically in a two stage assay can be routinely used for the determination of RuBP case activity instead of the radiometric method. The advantages and the validity of the method are discussed.
Istituto di Radiobiochimica ed Ecofisiologia Vegetali del C.N.R., Via Salaria Km. 29, 300, 00016 Monterotondo Scalo, Roma, Italy.
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Di Marco
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Tricoli