Kinetic Characterization of Stability

Decreases in the activity of an enzyme as a function of time, at different temperatures, are shown in Table 12.2 and Fig. 12.15a. Assuming that enzyme inactivation can be modeled as a first-order process, data can be linearized using Eq. (12.5) (Fig. 12.156). The slopes of the lines in Fig. 12.146 correspond to the first-order rate constant of denaturation ki)). As the temperature increases, so does the rate of inactivation, which is mirrored in increases in ku (Fig. 12.16a). The Arrhenius model can then be used to determine the energy of activation (Ea) of denaturation and estimate the value of the frequency factor, Ea = 48, 9 kJ mol and 

9 X 10 min (Fig. 12.16 ). As discussed previously, the decimal reduction time (D) is merely the inverse of the first-order reaction rate constant. From knowledge of the temperature dependence of the D value of an enzyme (Fig. 12.17a), the Z value can easily be determined Z = 33.5 °C (Fig. 12.17 ). 

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