Regulation by Competitive Binding

This model is essentially the same as the model discussed in section 2.8.6. Let A be the substrate on which the enzyme E acts to produce the product P. 

Let B be an inhibitor that binds to the same active site on which A also binds. The simplest PF of such an enzyme is 

We now choose an arbitrary level of occupancy, say 9a 0.8, to serve as our reference for the activity of the enzyme. If the occupancy of the enzyme is above 0.8, we shall say that the enzyme is fully active. If it is below, say, 0.2, we shall say that it is not active. 

FIGURE 3.21. Binding and regulatory curves for the competitive model, (a) 9 as a function of for various values of (these are indicated next to each curve), based on Eq. (3.7.4) with 7 = 1 and qs = 10. (b) The regulatory curve for the same model, with 9 as a function of As, based on Eq. (3.7.7). This function is the drop of the value of 9a in (a) along the vertical line at the point AJ. 

This level of occupancy (i.e., 6a 0.8) is attained by the enzyme in the absence of inhibitor B when A fulfills the equality 

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