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Título : Pyruvate kinase revisited. the activating effect of k+
Creador: Oria Hernández Jesús
Nivel de acceso: Open access
Palabras clave : Escherichia coli - Enzymology
Potassium - pharmacology
Piruvato Quinasa - Metabolism
Escherichia coli - Enzymology
Potassium - Pharmacology
Pyruvate Kinase - Metabolism
Descripción : For more than 50 years, it has been known that K(+) is an essential activator of pyruvate kinase (Kachmar, J. F., and Boyer, P. D. (1953) J. Biol. Chem. 200, 669-683). However, the role of K(+) in the catalysis by pyruvate kinase has not been totally understood. Previous studies without K(+) showed that the affinity of ADP-Mg(2+) depends on the concentration of phosphoenolpyruvate, although the kinetics of the enzyme at saturating K(+) concentrations show independence in the binding of substrates (Reynard, A. M., Hass, L. F., Jacobsen, D. D. & Boyer, P. D. (1961) J. Biol. Chem. 236, 2277-2283). Here, we explored the kinetics of the enzyme with and without K(+). The results show that without K(+), the kinetic mechanism of pyruvate kinase changes from random to ordered with phosphoenol-pyruvate as first substrate. V(max) with K(+) was about 400 higher than without K(+). In the presence of K(+), the affinities for phosphoenol-pyruvate, ADP-Mg(2+), oxalate, and ADP-Cr(2+) were 2-6-fold higher than in the absence of K(+). This as well as fluorescence data also indicate that K(+) is involved in the acquisition of the active conformation of the enzyme, allowing either phosphoenolpyruvate or ADP to bind independently (random mechanism). In the absence of K(+), ADP cannot bind to the enzyme until phosphoenolpyruvate forms a competent active site (ordered mechanism). We propose that K(+) induces the closure of the active site and the arrangement of the residues involved in the binding of the nucleotide
Colaborador(es) u otros Autores: Cabrera Nallely
Pérez Montfort Ruy
Ramírez Silva Leticia
Fecha de publicación : 2005
Tipo de publicación: Artículo
Formato: pdf
Identificador del Recurso : 10.1074/jbc.M508490200
Fuente: J Biol Chem 280(45):37924-37929
URI : http://repositorio.pediatria.gob.mx:8180/handle/20.500.12103/2749
Idioma: eng
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