Effect of Physical Factors on Reactions of Horse-Radish Peroxidase Complexes with Reduced Cytochrome c

Abstract

This investigation concerns the effect of certain physical factors-viscosity, dielectric constant, ionic strength, and temperature of the medium-on the reaction of hydrogen peroxide and ferrocytochrome c in the presence of the enzyme horse-radish peroxidase. From study of the effects of viscosity and dielectric constant, it was concluded that the reaction between the secondary complex of hydrogen peroxide and enzyme on the one hand and ferrocytochrome c on the other is controlled by diffusion in media of high viscosity and by electrostatic effects at low viscosities. With respect to ionic strength, the data at pH 4.7 indicated a dipole-dipole interreaction. The temperature dependence of the over-all reaction had a Q(10) of 1.25.

Influence of water activity and molecular mobility on peroxidase activity in salt and sorbitol–maltodextrin systems

“…This fact could be ascribed to the ionic nature of the ligand which could control the rate of enzymatic reaction at low viscosities by electrostatic effects, e.g. by influencing the ionic strength and the dielectric properties of the solvent (Farwell and Ackerman, 1963). Moreover, chloride, at high ionic strength, could inhibit the HRP activity by the sum of an unspecific and a specific interaction (Laurenti et al, 2000).…”

“…To this purpose, some authors (Farwell and Ackerman, 1963;Silver and Karel, 1981;Lim and Reid, 1991;Kerr et al, 1993;Kouassi and Roos, 2000) discussed the inhibition of enzymatic activity that occurs in concentrated food systems in terms of molecular mobility. In fact, in such systems, the rates of chemical reactions may become diffusion limited owing to decreased mobility; in this case the ability for reacting molecules to diffuse towards each other, rather than the barrier presented by the activation energy of the activated complex, is the rate limiting factor (Parker and Ring, 1995).…”

“…Enzymatic reactions are mainly controlled by diffusion in high viscosity aqueous solutions (Farwell and Ackerman, 1963;Cicerone and Soles, 2004) and the concentration of solutes was proven to influence the catalysis via change in the physical state of the system. On this basis, it is evident that water activity is not the only factor that influences the enzymatic activity in low moisture conditions, but other physical parameters, such as viscosity and glass transition temperature (T g ), which describe the molecular mobility within a system, should be taken into account (Kouassi and Roos, 2000;Bell, 2007).…”

“…The composition of the concentrated solutions was also studied, since the solutes could influence the protein mobility (Cicerone and Soles, 2004), as well as other properties of the solution (e.g. water activity, ionic strength and dielectric properties) which affect the enzymatic activity (Farwell and Ackerman, 1963;Bell, 2007). The water activity of the solutions was modified using either sodium chloride, a ionic ligand, or sorbitol, a non-ionic ligand, which are ingredients largely used in the food industry to deplete the water activity of foods, whilst the viscosity was modulated using maltodextrin.…”

Influence of Water Activity and System Mobility on Peroxidase Activity in Maltodextrin Solutions

“…9 -13 Enzymatic reactions are mainly controlled by diffusion in high viscosity aqueous solutions, and the concentration of co-solutes was proven to influence the catalysis via change in the physical properties of the system. 9,14 On this basis, it is evident that water activity is not the only factor that influences the enzymatic activity in low moisture conditions, but other physical parameters, such as viscosity and glass transition temperature (Tg), which scales the molecular mobility within a system, should be taken into account. 1,13 The most common correlation between viscosity and molecular mobility of a solute is provided by the Stokes relationship, where solute translational diffusion (D) is identified.…”