Hysteretic nature of phosphoenolpyruvate carboxylase isolated from maize.
The hysteretic nature of phosphoenolpyruvate carboxylase from maize was investigated at pH 7 by (a) transient kinetic studies, (b) kinetics of inhibition by 2-PG, a structural analog of PEP, and (c) effect of 2-PG on equilibrium binding of Mg2+. The lag time as a function of substrate concentration was nonlinear with an oblique asymptote. During steady state, cooperative kinetics for Mg2+ was changed to hyperbolic kinetics in the presence of 2-PG. Studies on the equilibrium binding of Mg2+ with the help of an external fluorescent probe, 8-anilino-6-naphthalinosulfonate showed that the hyperbolic binding of Mg2+ was changed to cooperative binding in the presence of 2-PG. On the basis of these results along with the results presented in the preceding paper, a fully concerted sequential model with subunit interaction is proposed for PEPC.
Jawali
N
N
Molecular Biology and Agriculture Division, Bhabha Atomic Research Centre, Trombay, Bombay, India.
D002262:Carboxy-Lyases / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008024:Ligands; D046911:Macromolecular Substances; D015636:Magnesium Chloride / Q000494:pharmacology; D008961:Models, Structural; D008962:Models, Theoretical; D010730:Phosphoenolpyruvate Carboxylase / Q000302:isolation & purification / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D003313:Zea mays / Q000201:enzymology*
D008024:Ligands; D046911:Macromolecular Substances; D015636:Magnesium Chloride; D002262:Carboxy-Lyases; D010730:Phosphoenolpyruvate Carboxylase