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. 1976 Jun;57(6):906–910. doi: 10.1104/pp.57.6.906

Purification and Characterization of Phosphoenolpyruvate Carboxylase from Maize Leaves 1

Kohji Uedan a, Tatsuo Sugiyama a
PMCID: PMC542146  PMID: 16659596

Abstract

Phosphoenolpyruvate carboxylase has been purified to homogeneity from maize (Zea mays L. var. Golden Cross Bantam T51) leaves. The ratio of specific activities in crude extracts and the purified enzyme suggests that the enzyme is a major soluble protein in the tissue. The enzyme has a sedimentation coefficient (s20,w) of 12.3S and a molecular weight, determined by sedimentation equilibrium, of 400,000 daltons. Dissociation of the enzyme and electrophoresis on dodecyl sulfate polyacrylamide gels yields a single stained band which corresponds to a subunit weight of 99,000 daltons. Thus it appears that the native enzyme is composed of four identical or similar polypeptide chains.

The enzyme yields cooperative rate-concentration plots (Hill number of 2) with phosphoenolpyruvate as the variable substrate at pH 7. This cooperativity disappears in the presence of an activator, glucose-6-P, or by raising the pH of the assay mixture to 8. Glycerol (20%, v/v) exerts a similar effect. The enzyme is also activated in the presence of glycine which causes an increase in Vmax without significant effect on the apparent Km for phosphoenolpyruvate and Hill number. The apparent Km for HCO3− is 0.02 mm, and the activation constant for Mg2+ is 1.54 mm at pH 7. There is an abrupt discontinuity in Arrhenius plots and an associated increase in activation energy below 10.8 C.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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