title: Effect of Mn2+ on fructose 2,6-bisphosphate inhibition of mouse liver, intestinal, and muscle fructose-1,6-bisphosphatases.
abstract: Fructose 2,6-bisphosphate inhibited all three fructose-1,6-bisphosphatases from the liver, intestine, and muscle of the mouse. The sensitivity of the liver enzyme to the inhibitor was significantly diminished when Mg2+ was replaced by Mn2+ as the activating cation. Inhibition of the liver enzyme by fructose 2,6-bisphosphate decreased as the concentration of the metal activator, Mn2+ or Mg2+, increased. The respective I50 values obtained by extrapolation of metal ion concentrations to zero were 40 microM with Mn2+ and 0.25 microM with Mg2+. The extent of desensitization to either fructose 2,6-bisphosphate or AMP inhibition by Mn2+ decreased in the order of the liver, intestine, and muscle enzyme. Only in the case of the liver enzyme was the substrate cooperativity induced by fructose 2,6-bisphosphate in the presence of Mg2+. In all three isoenzymes from the mouse, fructose 2,6-bisphosphate greatly potentiated the AMP inhibition of the enzyme in the presence of either Mg2+ or Mn2+. The liver enzyme with Mn2+ in addition to Mg2+ was still active in the presence of less than 1 microM fructose 2,6-bisphosphate, even though AMP was present at 100-200 microM.
mesh_terms: D000249:Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D006597:Fructose-Bisphosphatase / Q000378:metabolism*; D005635:Fructosediphosphates / Q000494:pharmacology*; D006598:Hexosediphosphates / Q000494:pharmacology*; D007422:Intestines / Q000201:enzymology*; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology*; D051379:Mice; D009132:Muscles / Q000201:enzymology*; D009928:Organ Specificity
chemical_list: D005635:Fructosediphosphates; D006598:Hexosediphosphates; D007527:Isoenzymes; D000249:Adenosine Monophosphate; D008345:Manganese; C027652:fructose 2,6-diphosphate; D006597:Fructose-Bisphosphatase; D008274:Magnesium