INVESTIGADORES
IGLESIAS Alberto Alvaro
artículos
Título:
Interaction of Divalent Metal Ions with NADP malic Enzyme from Maize
Autor/es:
M.F. DRINCOVICH, A.A. IGLESIAS, C.S. ANDREO
Revista:
PHYSIOLOGIA PLANTARUM
Referencias:
Año: 1991 vol. 81 p. 462 - 466
ISSN:
0031-9317
Resumen:
Abstract
The effect of several metal ions on NADP+-malic enzyme (EC 1.1.1.40) purified from Zea mays L. leaves was studied Mg2+, Mn2+, Co2+ and Cd2+ were all active metal cofactors. The malic enzyme from maize has a moderately high intrinsic preference for Mn2+ relative to Mg2+ at pH 7.0 and 8.0 Negative cooperativity detected in the binding of Mg2+ at pH 7.0 and 8.0 and in the binding of Mn2+
at pH 7.0 suggests the existence of at least two binding sites with
different affinity. All of the activating metal ions have preference
for octahedral coordination geometry and have ionic radii of 0.861.09
Å. The ions that act as inhibitors are outside this range and/or are
incapable of octahedral coordination. Ba2+, Sr2+, Cd2+, Ca2+, Be2+, Ni2+, Cu2+, Zn2+, Co2+, Hg2+ showed mixed-type inhibition. The reciprocal of their K1
values follow the order of their apparence in the Irving-Williams
series of stability that derives in part from size effects. It is
suggested that the size of the ions may play a partial role in
determining the strength of the metal interaction.