Characterization of phosphoenolpyruvate carboxylase from mature maize seeds: Properties of phosphorylated and dephosphorylated forms

• Published in: Biochimie 2010-10, Vol.92 (10), p.1362-1370
• Main Authors: Černý, Martin, Doubnerová, Veronika, Müller, Karel, Ryšlavá, Helena
• Format: Article
• Language: English
• Subjects: Animals; Cattle; Cyclic AMP-Dependent Protein Kinases - pharmacology; Kinetics; Malates - pharmacology; Phosphoenolpyruvate carboxylase; Phosphoenolpyruvate Carboxylase - antagonists & inhibitors; Phosphoenolpyruvate Carboxylase - isolation & purification; Phosphoenolpyruvate Carboxylase - metabolism; Phosphorylation; Seed; Seeds - enzymology; Sigmoidal kinetics; Zea mays; Zea mays - enzymology
• ISSN: 0300-9084; 1638-6183
• DOI: 10.1016/j.biochi.2010.06.019

Phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) from mature maize seeds ( Zea mays L.) was purified to homogeneity and a final specific activity of 13.3 μmol min −1 mg −1. Purified PEPC was treated with phosphatase from bovine intestinal mucosa or protein kinase A to study its apparent phosphorylation level. Kinetic parameters of the enzyme reaction catalyzed by phosphorylated and dephosphorylated forms under different conditions were compared, as well as an effect of modulators. The enzyme dephosphorylation resulted in the change of hyperbolic kinetics to the sigmoidal one (with respect to PEP), following with the decrease of maximal reaction rate and the increase of sensitivity to l-malate inhibition. The hyperbolic kinetics of native PEPC present in dry maize seeds was not changed after the protein kinase A treatment, while it was converted to the sigmoidal one after dephosphorylation. Level of PEPC phosphorylation was not affected during seed imbibition.