Enzyme inactivation kinetics, influence

Immobilization influences reaction kinetics, decreasing the activity by enzyme inactivation and steric hindrance, as well as promoting mass transfer resistance. The influence of internal diffusion, for example, the diffusion of substrate from the bulk solution to the... 

Several factors must be considered when the experimental assay condi tions are developed. The reaction rate depends on the concentrations ol substrate, enzyme, and necessary cofactors. In addition, the reaction rate is under the influence of environmental factors such as pH, temperature, anti ionic strength. Enzyme activity increases with increasing temperature until the enzyme becomes denatured. The enzyme activity then decreases until all enzyme molecules are inactivated by denaturation. During kinetic mea surement, it is essential that the temperature of all reaction mixtures lx maintained constant. 

Thermal Inactivation of Peroxidase. To study thermostability of spinach peroxidase without the influence of cellular components, isolated peroxidase was heat treated in 0.1 M phosphate buffer (pH 6.0). The thermal inactivation curves are presented in Figure 6 and they showed biphasic kinetic curves m the range of 60-70 C. The spinach suspension and the extract (Figure 6b and c) also exhibited biphasic curves similar to that of isolated peroxidase (Figure 6a). The thermodynamic data were siunmarized in Table m. The results indicated that isolated peroxidase was more thermostable than those in the suspension or in the extract in the range of 50-80 t). However, z-value was 13 t) for isolated peroxidase which was less than those ( 18 TO) for both of the enzymes in the suspension or tiie extract The results showed that peroxidase isolated fix>m spinach responded differently to heating than the enzymes in the spinach extract or suspension. In Table IV, heat stabilities of peroxi-... 

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