Mn2+-sensitive and -insensitive forms of phosphoenolpyruvate carboxykinase (GTP).

R. I. Brinkworth, R. W. Hanson, F. A. Fullin, V. L. Schramm

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26 Scopus citations


Phosphoenolpyruvate carboxykinase (GTP) (EC from rat liver cytosol is activated by micromolar concentrations of Mn2+ under conditions where GTP is present as the MgGTP complex and free Mg2+ is present in excess. The purified, homogeneous enzyme rapidly loses the ability to be activated by Mn2+ upon storage, incubation with oxidized glutathione, or incubation with Mn2+. These changes are prevented by reducing agents. Under certain conditions, phosphoenolpyruvate carboxykinase (Mr = 72,000) co-purifies with a protein of Mr = 29,000. This complex co-elutes on gel permeation chromatography but can be separated by chromatography on GTP-agarose in the presence of Mn2+. The Mr = 29,000 protein stabilizes the activity of the enzyme and protects against the changes which lead to the loss of the Mn2+ activation. These results suggest that the Mn2+ activation of P-enolpyruvate carboxykinase is dependent on the degree of oxidation of cysteine sulfhydryls. The role of the Mr = 29,000 protein in in vitro experiments is to stabilize the enzyme oxidation state which permits activation by Mn2+.

Original languageEnglish (US)
Pages (from-to)10795-10802
Number of pages8
JournalJournal of Biological Chemistry
Issue number21
StatePublished - Nov 10 1981
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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