Embed Size (px)
Citation preview
Enzyme Action
Learning objective: to describe different models forenzyme action and to investigate factors which control the rate of an enzyme reaction
18th October
More free powerpoints at www.worldofteaching.com
Lock and Key
Lock and Key
However 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
ctio
n
Enzyme activity
Variable you are looking at
Enzyme activity
Four Variables
Enzyme activity
Four Variables
Temperature
pH
Enzyme Concentration
Substrate Concentration
Rat
e of
Rea
ctio
n
Temperature
Rat
e of
Rea
ctio
n
Temperature
0 20 30 5010 40 60
Rat
e of
Rea
ctio
n
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 protein
ACTIVE SITE CHANGES SHAPE SO SUBSTRATE NO LONGER FITS
Even if temperature lowered – enzyme can’t regain its correct shape
Rat
e of
Rea
ctio
n
pH
Rat
e of
Rea
ctio
n
pH
1 3 42 5 6 7 8 9
Rat
e of
Rea
ctio
n
pH
1 3 42 5 6 7 8 9
Narrow pH optima
Rat
e of
Rea
ctio
n
pH
1 3 42 5 6 7 8 9
Narrow pH optima
WHY?
Rat
e of
Rea
ctio
n
pH
1 3 42 5 6 7 8 9
Narrow pH optima
Disrupt Ionic bonds - Structure
Effect charged residues at activesite
Rat
e of
Rea
ctio
n
Enzyme Concentration
Rat
e of
Rea
ctio
n
Enzyme Concentration
Enzyme Concentration
Rat
e of
Rea
ctio
n
Substrate Concentration
Rat
e of
Rea
ctio
n
Substrate Concentration
Substrate Concentration
Rat
e of
Rea
ctio
n
Substrate Concentration
Substrate Concentration
Active sites full- maximum turnover
