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Alfalfa Root Nodule Carbon Dioxide Fixation: II. Partial Purification and Characterization of Root Nodule Phosphoenolpyruvate Carboxylase

Carroll P. Vance and Susan Stade
Plant Physiology
Vol. 75, No. 1 (May, 1984), pp. 261-264
Stable URL: http://www.jstor.org/stable/4268658
Page Count: 4
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Alfalfa Root Nodule Carbon Dioxide Fixation: II. Partial Purification and Characterization of Root Nodule Phosphoenolpyruvate Carboxylase
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Abstract

A nonphotosynthetic phosphoenolpyruvate carboxylase (EC 4.1.1.31) was partially purified from the cytosol of root nodules of alfalfa. The enzyme was purified 86-fold by ammonium sulfate fractionation, DEAE-cellulose, hydroxylapatite chromatography, and reactive agarose with a final yield of 32%. The enzyme exhibited a pH optimum of 7.5 with apparent Km values for phosphoenolpyruvate and magnesium of 210 and 100 micromolar, respectively. Two isozymes were resolved by nondenaturing polyacrylamide disc gel electrophoresis. Subsequent electrophoresis of these isozymes in a second dimension by sodium dodecyl sulfate slab gel electrophoresis yielded identical protein patterns for the isozymes with one major protein band at molecular weight 97,000. Malate and AMP were slightly inhibitory (about 20%) to the partially purified enzyme. Phosphoenolpyruvate carboxylase comprised approximately 1 to 2% of the total soluble protein in actively N2-fixing alfalfa nodules.

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