Enzyme Kinetics II

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Enzyme Kinetics II

• 10/16/2008

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Kinetic data cannot unambiguously establish a
reaction mechanism.
Although a phenomenological description can be
obtained the nature of the reaction intermediates
remain indeterminate and other independent
measurements are needed.
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Reaction MechanismsA Sequential Reactions

• All substrates must combine with enzyme before
  reaction can occur

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Bisubstrate reactions
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Random Bisubstrate Reactions
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Ping-Pong Reactions

• Group transfer reactions
• One or more products released before all
  substrates added

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Inhibition kinetics

• There are three types of inhibition kinetics
  competitive,
• mixed and uncompetitive.
• Competitive- Where the inhibitor competes with
  the substrate.

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Competitive Inhibition
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HIV protease inhibitors
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Competitive Inhibition Lineweaver-Burke Plot
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Uncompetitive Inhibition
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Uncompetitive Inhibition Lineweaver-Burke Plot
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Mixed inhibition
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Mixed inhibition is when the inhibitor binds to
the enzyme at a location distinct from the
substrate binding site. The binding of the
inhibitor will either alter the KM or Vmax or
both.
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The effect of pH on kinetic parameters
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Lecture 17Tuesday 10/21/08Enzyme Kinetics /
Exam II Minireview