Mn2+-sensitive and -insensitive forms of phosphoenolpyruvate carboxykinase (GTP).
Phosphoenolpyruvate carboxykinase (GTP) (EC 4.1.1.32) 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+.
D000818:Animals; D003600:Cytosol / Q000201:enzymology; D006160:Guanosine Triphosphate; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D046911:Macromolecular Substances; D008345:Manganese / Q000494:pharmacology*; D008970:Molecular Weight; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats
D007527:Isoenzymes; D046911:Macromolecular Substances; D008345:Manganese; D006160:Guanosine Triphosphate; D010729:Phosphoenolpyruvate Carboxykinase (GTP)