title: Purification and properties of phosphoenolpyruvate carboxykinase from Hymenolepis diminuta (Cestoda).
abstract: A method is described for the purification of the enzyme phosphoenolpyruvate carboxykinase (PEPCK) from the cestode Hymenolepis diminuta. When purified to electrophoretic homogeneity, the enzyme had a molecular weight of 70,600 and an isoelectric point of 7.5. Kinetic studies indicated that the pH 5.6 was optimal for the carboxylation reaction and that Mn++ was the preferred divalent cation; there was no activity of the enzyme in the presence of Mg++. Apparent Km values for the carboxylation reaction were determined; those for GDP (20.6 muM) and PEP (38.9 muM) were lower than the values previously reported. GTP, GMP, ITP, IMP, fumarate, succinate and alpha-ketoglutarate were found to be competitive inhibitors and their Ki values determined.
mesh_terms: D000818:Animals; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D006926:Hymenolepis / Q000201:enzymology*; D007526:Isoelectric Point; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D008970:Molecular Weight; D010728:Phosphoenolpyruvate / Q000378:metabolism; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D006153:Guanosine Diphosphate; D008345:Manganese; D010728:Phosphoenolpyruvate; D006160:Guanosine Triphosphate; D010729:Phosphoenolpyruvate Carboxykinase (GTP); D008274:Magnesium