Sar1 is the only GTPase switch protein activated at the ER membrane

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#Unit 1. Molecules and their Interaction Relevant to Biology

In more complicated systems, the primary plots may be linear but the secondary plots non-linear. For example, if not one but two molecules of inhibitor can bind to the substrate binding site, then parabolic competitive inhibition is said to occur, because of the shape of the secondary and Dixon plots.

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#Unit 1. Molecules and their Interaction Relevant to Biology

Similarly, if the inhibitor binds to a different site from the substrate and reduces the affinity of the enzyme for the substrate without altering the reaction characteristics of that substrate which does bind, then hyperbolic competitive inhibition results

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#Unit 1. Molecules and their Interaction Relevant to Biology

Dixon plot for competitive inhibition

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#Unit 1. Molecules and their Interaction Relevant to Biology

TLS Online TPP Program

#Id: 8561

#Unit 1. Molecules and their Interaction Relevant to Biology

Uncompetitive inhibitors bind only to the enzyme-substrate complex and not to the free enzyme. 

TLS Online TPP Program

#Id: 8562

#Unit 1. Molecules and their Interaction Relevant to Biology

In neither case does the inhibitor compete with the substrate for the same binding site, so the inhibition cannot be overcome by increasing the substrate concentration.