INVESTIGADORES
GONZALEZ Daniel Hector
artículos
Título:
Changes in the quaternary structure of phosphoenolpyruvate carboxylase induced by ionic strength affect its catalytic activity
Autor/es:
WAGNER, RICHARD; GONZALEZ, DANIEL H.; PODESTÁ, FLORENCIO E.; ANDREO, CARLOS S.
Revista:
EUROPEAN JOURNAL OF BIOCHEMISTRY
Editorial:
Elsevier
Referencias:
Año: 1987 vol. 164 p. 661 - 666
ISSN:
0014-2956
Resumen:
Phosphoenolpyruvate carboxylase from maize leaves dissociated into
dimers and/or monomers when exposed to increasing ionic strength (e.g.
200-400 mM NaCl) as indicated by gel filtration experiments. Changes in
the oligomerization state were dependent on pH, time of preincubation
with salt and protein concentration. A dissociation into dimers and
monomers was observed at pH 8, while at pH 7 dissociation into the
dimeric form only was observed. Exposure of the enzyme to higher ionic
strength decreased the activity in a time-dependent manner. Turnover
conditions and glucose 6-phosphate protected the carboxylase from the
decay in activity, which was faster at pH 7 than at pH 8. The results
suggest that changes in activity of the enzyme, following exposure to
high ionic strength, are the consequence of dissociation. Tetrameric and
dimeric forms of the phosphoenolpyruvate carboxylase seemingly reveal
different catalytic properties. We suggest that the distinct catalytic
properties of the different oligomeric species of phosphoenolpyruvate
carboxylase and changes in the equilibrium between them could be the
molecular basis for an effective regulation of metabolite levels by this
key enzyme of C 4 plants.