Kinetic parameters for thermal inactivation of soluble peroxidase from needles of Serbian spruce Picea omorika (Pancić) Purkyne.

Thermal inactivation of peroxidase (POD) in an extract of Picea omorika (Pancić) Purkyne needles initiated by heat treatment was studied. This is the first study of this kind on a conifer species. Non-linear regression analysis was applied on the inactivation rate data, combining Mitscherlich and Arrhenius equations, treating time and temperature simultaneously as explaining variables. We determined the inactivation rate constant k, the Arrhenius energy of inactivation E and the remaining activity C(min) for the crude extract and for separated acidic and basic enzyme fractions, as well as for individual isoenzymes separated electrophoretically. A comparison of inactivation parameters for acidic and basic fractions shows that the thermal inactivation rate of the basic fraction is higher. The obtained value of inactivation energy for crude extract was between the values for acidic and basic isoenzyme fractions. One of the three analysed individual isoenzymes was characterised by a lower inactivation rate constant and higher inactivation energy. Another isoenzyme showed considerably higher level of remaining activity compared to the others, which identified it as the most resistant to high temperatures. The acquired values of Arrhenius energy of inactivation for POD in crude extract were intermediate, considering a range of POD values for various other plant species.