enzymes models of action 2
TRANSCRIPT
Enzyme ActionLearning objective: to describe different models forenzyme action and to investigate factors which control the rate of an enzyme reaction
18th October
Lock and Key
Lock and KeyHowever certain substances can bind to the enzyme at sites other than theActive site and modify its activity (inhibitors/co-factors)
Idea that the enzyme is flexible
Induced Fit
Enzyme reactions
enzyme + substrate enzyme-substrate complex
Enzyme reactions
enzyme + substrate enzyme-substrate complex
E +S ES
Enzyme reactions
enzyme + productenzyme-substrate complex
E +PES
enzyme + substrate enzyme-substrate complex
E +S ES
Enzyme activity
How fast an enzyme is workingRate of Reaction
Enzyme activity
How fast an enzyme is workingRate of Reaction
Rate of Reaction = Amount of substrate changed (or amount product formed) in a given period of time.
Rat
e of
Rea
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Enzyme activity
Variable you are looking at
Enzyme activity
Four Variables
Enzyme activity
Four Variables
Temperature
pH
Enzyme Concentration
Substrate Concentration
Rat
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Temperature
Rat
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Temperature
0 20 30 5010 40 60
Rat
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Temperature
0 20 30 5010 40 60
40oC - denatures
5- 40oC Increase in Activity
<5oC - inactive
Effect of heat on enzyme activtyIf you heat the protein above its optimal temperature
bonds break meaning the protein loses it secondary and tertiary structure
Effect of heat on enzyme activty
Denaturing the protein
Effect of heat on enzyme activty
Denaturing the proteinACTIVE SITE CHANGES SHAPE
SO SUBSTRATE NO LONGER FITS
Even if temperature lowered – enzyme can’t regain its correct shape
Rat
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pH
Rat
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pH
1 3 42 5 6 7 8 9
Rat
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pH
1 3 42 5 6 7 8 9
Narrow pH optima
Rat
e of
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pH
1 3 42 5 6 7 8 9
Narrow pH optima
WHY?
Rat
e of
Rea
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pH
1 3 42 5 6 7 8 9
Narrow pH optima
Disrupt Ionic bonds - Structure
Effect charged residues at activesite
Rat
e of
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Enzyme Concentration
Rat
e of
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Enzyme Concentration
Enzyme Concentration
Rat
e of
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Substrate Concentration
Rat
e of
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Substrate Concentration
Substrate Concentration
Rat
e of
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Substrate Concentration
Substrate Concentration
Active sites full- maximum turnover
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