Differences in effect of Mn(II), Fe(III), Co(II), and Zn(II) ions on trypsinogen activation

The influence of Mn2+, Fe3+, Co2+, and Zn2+ ions on the extent of trypsinogen activation has been determined for several ion concentrations at pH 7.4 and 36.4 degrees C. For the Mn2+ ion also the autocatalytic rate constants have been detected. The effect of Ca2+ has been reinvestigated for comparison purposes. The apparent dissociation constants of KMn2+ = 0.01 (M) and KCa2+ = 0.02 (M) have been found for the given metal ion-trypsinogen complexes. For Co2+ ion, however, only a slight effect and for Fe3+ and Zn2+ ions no significant effect could be detected on trypsinogen activation. The investigated ions are of empty, open, and completed d subshells of electrons and they are different also in their ionic size. The differences in effects of the ions are discussed on the basis of these factors.