title: Characterization of phosphoenolpyruvate carboxylase from mature maize seeds: properties of phosphorylated and dephosphorylated forms.
abstract: 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.
authors.affiliation: Department of Biochemistry, Faculty of Science, Charles University, Hlavova 2030, Prague 2 128 40, Czech Republic.
authors.forename: Martin
authors.initials: M
authors.lastname: Cerný
authors.forename: Veronika
authors.initials: V
authors.lastname: Doubnerová
authors.forename: Karel
authors.initials: K
authors.lastname: Müller
authors.forename: Helena
authors.initials: H
authors.lastname: Ryšlavá
mesh_terms: D000818:Animals; D002417:Cattle; D017868:Cyclic AMP-Dependent Protein Kinases / Q000494:pharmacology; D007700:Kinetics; D008293:Malates / Q000494:pharmacology; D010730:Phosphoenolpyruvate Carboxylase / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D010766:Phosphorylation; D012639:Seeds / Q000201:enzymology*; D003313:Zea mays / Q000201:enzymology*
chemical_list: D008293:Malates; C030298:malic acid; D017868:Cyclic AMP-Dependent Protein Kinases; D010730:Phosphoenolpyruvate Carboxylase