Phosphorylation of pyruvate kinase type K is restricted to the dimeric form.
Biochim Biophys Acta
; 1121(1-2): 61-8, 1992 May 22.
Article
en En
| MEDLINE
| ID: mdl-1599952
ABSTRACT
In the absence of glycolytic intermediate, fructose-1,6-bisphosphate, pyruvate kinase type K exists in the dimeric form and is readily phosphorylated, whereas in the same sample and the same conditions pyruvate kinase type M is present as a tetramer and is not phosphorylated. Addition of fructose-1,6-bisphosphate results in the association of dimeric K2 molecules to a tetrameric K4 enzyme as determined by gel filtration and cellulose acetate electrophoresis, with concomitant loss of the capacity of the K isozyme to become phosphorylated. Phosphorylated K2 dimers can also tetramerize, but with a low recovery of the radiolabel, suggesting a fructose-1,6-bisphosphate induced dephosphorylation or selective degradation. The dimeric K isozyme is enzymatically active; inactive K-type monomers can be detected by immunoblot analysis in the absence of fructose-1,6-bisphosphate, but no phosphorylated pyruvate kinase is present in this fraction. The formation of K4 tetramers can not be accomplished by the substrate phosphoenolpyruvate. Fructose-1,6-bisphosphate is an allosteric activator of pyruvate kinase type K and induces hyperbolic saturation curves for phosphoenolpyruvate. In contrast, in the absence of effectors, pyruvate kinase type M exhibits Michaelis-Menten kinetics, but sigmoidal curves can be induced by the amino acid phenylalanine. However, even in the presence of phenylalanine, the M-type maintained its tetrameric configuration and did not serve as a substrate in the phosphorylation reaction. These findings argue for the importance of subunit interaction in the regulation of phosphorylation of pyruvate kinase.
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Banco de datos:
MEDLINE
Asunto principal:
Piruvato Quinasa
/
Astrocitoma
/
Bazo
/
Encéfalo
/
Fructosadifosfatos
/
Isoenzimas
/
Músculos
Límite:
Humans
/
Male
/
Middle aged
Idioma:
En
Revista:
Biochim Biophys Acta
Año:
1992
Tipo del documento:
Article
País de afiliación:
Países Bajos