The copper- and zinc-containing superoxide dismutase from Escherichia coli: molecular weight and stability.
Arch Biochem Biophys
; 340(2): 305-10, 1997 Apr 15.
Article
en En
| MEDLINE
| ID: mdl-9143335
The periplasmic Cu,Zn superoxide dismutase (Cu,ZnSOD) from Escherichia coli has been shown by sedimentation equilibrium to be a monomer with a molecular weight of approximately 17,000. The enzyme suffered a reversible inactivation when heated to 70 degrees C. This was minimized by added Cu(II) or Zn(II). Heat lability was greater in phosphate than in Tris buffer. The enzyme exhibited a time-dependent inactivation by Hg(II) and this too was greater in phosphate than in Tris. This behavior can be explained by a modest affinity of the enzyme for Cu(II) and Zn(II) which results in a dissociation/association equilibrium. Elevation of the temperature shifts this equilibrium toward dissociation and phosphate sequesters the released metals making them less available for reinsertion at the active site. Hg(II) competes for occupancy of the active site and there were more unoccupied sites in phosphate than in Tris. A parallel was drawn between the E. coli Cu,ZnSOD and FALS varients of human Cu,ZnSOD, which are also relatively unstable and exhibit low affinity for Cu(II).
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Superóxido Dismutasa
/
Escherichia coli
Idioma:
En
Revista:
Arch Biochem Biophys
Año:
1997
Tipo del documento:
Article
País de afiliación:
Estados Unidos
Pais de publicación:
Estados Unidos