06OtherAspectsofSingleEnzymeReactions

06OtherAspectsofSingleEnzymeReactions - Reversible...

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Reversible Inhibition Competitive V max [S] K m (1 + ) + [S] v = [I ] K I 2 Competitive Inhibition E + S ES E + P + I EI k 1 k -1 k 2 K I V max [S] K m (1 + ) + [S] v = [ I ] K I or K i K i You expect TS analog inhibitors to be competitive inhibitors. So how would you tell?
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3 In uncompetitive inhibition , the inhibitor binds only to the enzyme-substrate complex. E + S ES E + P k 1 k -1 k 2 + I ESI K’ I K’ I = [ ES ] [ I ] [ ESI ] Uncompetitive Inhibition 4 All lines have identical slopes and are parallel. Uncompetitive inhibitors alter both the K m and the V max . 0 2 4 6 8 10 12 14 16 18 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3 [ I ] = 2 [ I ] = 1 [ I ] = 0 1 / velocity 1 / [ S ] Uncompetitive Inhibition
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5 In noncompetitive inhibition , the inhibitor binds to both the enzyme alone and to the enzyme-substrate complex. E + S ES E + P + I EI k 1 k -1 k 2 K I K I = [ E ] [ I ] [ EI ] + I ESI K’ I K’ I = [ ES ] [ I ] [ ESI ] Also referred to as mixed inhibition . Noncompetitive Inhibition 6 Noncompetitive inhibitors alter V max but do not change K m . All lines intersect at the x axis same 1 / K m . 0 5 10 15 20 25 30 35 - 1 - 0 . 500 . 511 . 522 . 53 [ I ] = 2 [ I ] = 1 [ I ] = 0 1 / velocity 1 / [ S ] 1 K m Noncompetitive Inhibition
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7 Get from arrows to equation for Un-competitive and Non-competitive (mixed) Inhibition [] ES k v 2 = Rate expression Equilibrium expressions Enzyme Mass Balance [ ES ] = ? V max [S] K m (1 + ) + [S] v = [I ] K I [S](1 + ) K I V max [S] K m + [S](1 + ) v = K I 8 Reversible Inhibition Competitive Uncompetitive Noncompetitive V max [S] K m (1 + ) + [S] v = K I V max [S] K m (1 + ) + [S] v = K I V max [S] K m + [S](1 + ) v = K I [S](1 + ) K I
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9 How to get data, and then from data to Ki 10
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This note was uploaded on 03/03/2009 for the course BIOMEDE 321 taught by Professor Takayama during the Winter '08 term at University of Michigan.

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06OtherAspectsofSingleEnzymeReactions - Reversible...

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