title: The roles of magnesium ions in the reaction catalysed by phosphofructokinase from Trypanosoma brucei.
abstract: The involvement of Mg2+ ions in the reaction catalysed by phosphofructokinase from Trypanosoma brucei was studied. The true substrate for the enzyme was shown to be the MgATP2-complex, and free Mg2+ ions are also required for enzyme activity. At concentrations of MgATP2- of 2.92 mM and greater, and a fructose 6-phosphate concentration of 1 mM and in the presence of EDTA as a Mg2+ buffer, the Km value for Mg2+ was determined to be 294 +/- 18 microM. Neither MgATP nor free ATP is an inhibitor of the enzyme, although apparent inhibition by the latter can be observed as a consequence of the decrease in free Mg2+ by chelation.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects; D005636:Fructosephosphates / Q000494:pharmacology; D008274:Magnesium / Q000378:metabolism*; D008345:Manganese / Q000494:pharmacology; D010732:Phosphofructokinase-1 / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000187:drug effects / Q000201:enzymology*
chemical_list: D005636:Fructosephosphates; D008345:Manganese; C027618:fructose-6-phosphate; D000255:Adenosine Triphosphate; D010732:Phosphofructokinase-1; D008274:Magnesium