Mg dependence and other properties of fructose-1, 6-diphosphatase and glucose-6-phosphatase in various organs of cattle]

The properties of fructose-1.6-disphosphatase in supernatant of homogenate of liver, kidneys, and adductor muscles of cattle were tested. EDTA was found to activate the enzyme up to concentrations of 10 mMol. The pH optimum was 7.5 in the presence of EDTA. Even lower concentrations of magnesium ions caused activation of the enzyme, but an activating effect was obtained as well from relatively high Mg concentrations. Fructose-1.6-diphosphatase could by activated also by 0.2 mMol Mn or Co ions or 1 mMol Zn ions. Inhibitive action was obtained from Cu, Cd, Pb, and Hg ions. Microsomal fractions of cattle liver and kidney caused high activity of glucose-6-phosphatase, but only low action was obtained be using microsomal fractions of mesenteric mucous membrane or brain. Mg ions, basically, failed to trigger activation, and higher concentrations even caused inhibition. The relatively high activity of both fructose-1.6-diphosphatase and glucose-6-phosphatase in kidney of cattle appeared to suggest an involvement of those enzymes in gluconeogenesis.