Hyperbolic inhibition in monosubstrate reactions

Inhibition of monosubstrate enzyme reactions with an inhibitor may be expressed in a more general way  

In reaction (6.1), we have admitted that the enzyme can form an EAI complex that can yield product with equal or less facility than can the EA complex. In this case, the apparent values of and C a/Yi) functions will display a 

In addition, we have admitted that El complex may have different affinities for the substrate than the free enzyme, and that EA complex may have different affinities for the inhibitor than the free enzyme. A rate equation for this general case may be derived from the rapid equilibrium assumptions  

Eiquation (6.2) is quite general, and it describes a number of different inhibition mechanisms, including the simple linear inhibition mechanisms desaibed in Chapter 5. Thus, a = i and fi = o describe a simple linear noncompetitive inhibition (Section 5.3), and when a = we have a simple linear competitive inhibition (Section 5.2). 

An infinitely high A will drive aU the enzyme to a mixture of EA and EAI, and at infinitely high I all the enzyme will be converted to El and EAI. Because EAI can form the product, the velocity cannot be driven to zero by increasing I (Fig. 1). This clearly shows that the nonlinear inhibition is not a complete inhibition, as the velocity does not approach zero even at higher concentrations of an inhibitor. 

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