EN
Fluorine exists in hard tissues (bones, teeth), in which it plays a structural function. Small quantities of fluorine are found in biological solvents and soft tissues. Fluoride ions are not enzyme cofactors but may influence their activity. In this paper, the acitivity of ICDH (isocitric dehydrogenase, E. C. 1.1.1.42) was tested in the presence of different concentrations of fluoride ions (from 0.05 to 5.0 μmol/l). Simultaneously, we studied ICDH activity in the presence of (acide from fluorine) magnesium and zinc ions. ICDH (of the Sigma) was tested by colorimetrical method. Fluoride ions in a range of concentrations from 0.05 to 0.52 μmol/1 have an inhibition effect, but in concentrations of 1.5 to 5.0 μmol/l activate the tested enzyme. The magnesium ions added to the incubation mixture eliminated the inhibition and activation effects of fluoride ions on the ICDH.