Complex Mechanisms of Enzyme Inactivation

If enzyme inactivation is described by a one-step first-order mechanism, exponential decay of enzyme activity ensues, so that a straight line should be obtained in a semilog plot of residual activity versus time, as suggested by Eq. 3.126. Despite its limitation, this model has been used (and sometimes abused by forcing the data) to describe enzyme inactivation. It is quite frequent to observe behaviors that clearly depart from that simple model as revealed by semilog residual activity versus time profiles of the following type  

Sadana 1986 Ulbrich and Schellenberger 1986 Abraham et al. 1992). The inactivation profile results from the superposition of the (exponential) decays of each enzyme species (Dagys et al. 1984). 

One-step first order, parallel (Dagys et al. 1984) and series (Henley and Sadana 1985) mechanisms of inactivation are then particular cases of this generalized model. 

The inactivation rate constant and its temperature dependence can be experimentally determined as already presented in section 3.5.2. 

This mechanism is represented by the first column (n = 1) of the generalized scheme, so that ay = 0 and ky = 0 for all j 1. According to that scheme, Eq. 5.41 reduces to  

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