Enzyme Action Learning objective: to describe different models for enzyme action and to investigate factors which control the rate of an enzyme reaction
Lock and Key
Lock and Key However certain substances can bind to the enzyme at sites other than the Active 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 + substrate enzyme-substrate complex E +S ES enzyme + product enzyme-substrate complex ES E +P
How fast an enzyme is working Enzyme activity How fast an enzyme is working Rate of Reaction
How fast an enzyme is working Enzyme activity How fast an enzyme is working Rate of Reaction Rate of Reaction = Amount of substrate changed (or amount product formed) in a given period of time.
Enzyme activity Rate of Reaction Variable you are looking at
Enzyme activity Four Variables
Enzyme activity Temperature pH Enzyme Concentration Four Variables Enzyme Concentration Substrate Concentration
Temperature Rate of Reaction
Temperature Rate of Reaction 10 20 30 40 50 60
Temperature 5- 40oC Increase in Activity 40oC - denatures Rate of Reaction 10 20 30 40 50 60 <5oC - inactive
Effect of heat on enzyme activty If 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
pH Rate of Reaction
pH Rate of Reaction 1 2 3 4 5 6 7 8 9
pH Narrow pH optima Rate of Reaction 1 2 3 4 5 6 7 8 9
pH Narrow pH optima WHY? Rate of Reaction 1 2 3 4 5 6 7 8 9
Effect charged residues at active pH Narrow pH optima Disrupt Ionic bonds - Structure Rate of Reaction Effect charged residues at active site 1 2 3 4 5 6 7 8 9
Enzyme Concentration Rate of Reaction
Enzyme Concentration Rate of Reaction Enzyme Concentration
Substrate Concentration Rate of Reaction
Substrate Concentration Rate of Reaction Substrate Concentration
Substrate Concentration Active sites full- maximum turnover Rate of Reaction Substrate Concentration