Ribulose 1,5-diphosphate Carboxylase from Oenothera. Purification and a Peptide Mapping Procedure for the Subunits

Ribulose 1,5-diphosphate carboxylase has been purified from fully expanded leaves of Oenothera. The isolation procedure overcame the problems which resulted from a high content of mucilage and phenolic compounds in the leaves. Protein extraction into dilute buffer containing a phenol adsorbant and reducing agents followed by a combination of gel filtration and ion exchange chromatography allowed the enzyme to be essentially purified to homogeneity. The purified RuDP carboxylase had a specific activity of 1.5 i.tmoles CO2 fixed, min -~. mg -~ at pH 7.8 and 25 ~ The two subunits could be dissociated in detergent solutions and were found to have molecular weights and amino acid compositions similar to the respective subunits from other sources. A two-dimensional mapping procedure employing ion exchange and paper chromatography was used to partially characterize the tryptic peptides of the RuDP carboxylase subunits; this technique may be useful in interspecific comparisons of the primary structure of the two subunits from Oenothera species.