The purification of fructose 1,6-diphosphatase from ox liver and its activation by ethylenediaminetetra-acetate.

1.A procedure for the purification of ox liver fructose 1,6-kiphosphatase is described. A number of criteria indicate that the enzyme was not subjected to any significant degree of proteolytic attack during the purification. 2. The molecular weight, amino acid composition and subunit molecular weight are reported. 3. The activation by EDTA was shown to be due to the chelation heavy metals rather than by a more complex interaction with the enzyme as had previously been suggested.     

Effect of calcitonin on fructose 1,6-diphosphatase activity in rat liver: role of cytosolic calcium concentration

The effect of calcitonin (CT) on fructose 1,6-diphosphatase activity in the hepatic cytosol was investigated after a single subcutaneous administration of the hormone to rats. Administration of CT (synthetic [Asu1,7] eel CT; 80 MRC mU/100 g body weight) produced significant increase in fructose 1,6-diphosphatase activity and calcium content in the hepatic cytosol of intact and thyroparathyroidectomized rats. Those alterations were also observed with the dose of CT at physiological level. The binding of calcium by 10 microM EGTA in the hepatic cytosol caused a clear reduction of the increase in fructose 1,6-diphosphatase activity produced by CT administration. The enzyme activity of CT-treated rats was markedly reduced by W-7 (100 microM), calmodulin inhibitor, while that of control rats was not significantly altered by the drug. Meanwhile, fructose 1,6-diphosphatase activity in the hepatic cytosol obtained from normal rats was significantly enhanced by addition of calcium ion (0.1-5.0 microM). This increase was also clearly inhibited by W-7. These results suggest that CT increases fructose 1,6-diphosphatase activity in the hepatic cytosol of rats, and that this hormonal regulation may depend on calmodulin, mediated through calcium increased in the cytosol.