INFLUENCE OF MONO-CATION AND DIVALENT-CATION ON THERMOSTABILITY OF LACTOPEROXIDASE IN MODEL SYSTEMS

The influence of mono- and divalent cations and heat treatment on lact operoxidase activity was examined. Solutions of NaCl, KCl, CaCl2 and M gCl2 at different concentrations ranging from 0.05 to 1 M and containi ng 20 mu g/ml of lactoperoxidase were prepared and heated at 60 degree s C and 72 degrees C for definite periods of time. Residual enzymic ac tivity was then measured. According to the data, lactoperoxidase therm ostability is considerably influenced by type and concentration of cat ion. Ca++ and Mg++ have a stabilizing effect greater than that of N-a and K+ at low concentrations, but they have the contrary effect at hi gh concentrations. Based on these results, it is clear that the mechan ism involved in heat inactivation of the enzyme with monovalent cation s is different from that involved with divalent cations.