title: Interaction of anions and divalent metal ions with phosphoenolpyruvate carboxykinase.
abstract: The catalytic activity of phosphoenolpyruvate carboxykinase in rat liver cytosol is stimulated by incubating with Fe2+, Mn2+, Co2+, and Cd2+. When purified, the enzyme no longer responds to Fe2+, Co2+, or Cd2+ but retains a response to Mn2+. Low concentrations of SO4(2-) in the incubation medium with enzyme and divalent transition metal allow stimulation by Fe2+ and Co2+ and enhance the response to Mn2+. Under identical conditions, orthophosphate with Fe2+ is a potent inhibitor of the enzyme (half-maximal inhibition at 50 muM). A thiol is required in the incubation medium for the effects of Fe2+ plus sulfate or orthophosphate to be expressed. The magnitude of these effects depends on the thiol concentration. Dithiothreitol is more effective than GSH and activation by sulfate plus Fe2+ appears to require the reduced form of dithiothreitol. Sulfate ion is not considered to be the physiological Fe2+-activator of P-enolpyruvate carboxykinase in rat liver cytosol, as this function is fulfilled by a newly discovered liver protein. Knowledge concerning the interaction of Fe2+ and sulfate with the enzyme may be useful in examining their interaction between the enzyme, ferrous ion, and this activator protein.
mesh_terms: D000085:Acetates / Q000494:pharmacology; D000818:Animals; D000838:Anions; D002104:Cadmium / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002413:Cations, Divalent; D003035:Cobalt / Q000494:pharmacology; D003600:Cytosol / Q000201:enzymology; D004229:Dithiothreitol / Q000494:pharmacology; D005290:Ferric Compounds / Q000494:pharmacology; D005296:Ferrous Compounds / Q000494:pharmacology; D008099:Liver / Q000201:enzymology; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D009566:Nitrates / Q000494:pharmacology; D010710:Phosphates / Q000494:pharmacology; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000378:metabolism*; D051381:Rats; D013431:Sulfates / Q000494:pharmacology
chemical_list: D000085:Acetates; D000838:Anions; D002413:Cations, Divalent; D005290:Ferric Compounds; D005296:Ferrous Compounds; D009566:Nitrates; D010710:Phosphates; D013431:Sulfates; D002104:Cadmium; D003035:Cobalt; D008345:Manganese; D010729:Phosphoenolpyruvate Carboxykinase (GTP); D008274:Magnesium; D002118:Calcium; D004229:Dithiothreitol