Enzyme kinetics Flashcards
What is the Vmax?
The maximum rate of a reaction for an enzyme as it is fully saturated by substrate.
What is Km?
50% of the Vmax
What is Km equivalent to ?
The substrate concentration in moles.
What does the Michaelis-Menten kinetic model do?
Create relationship between the concentration for the substrate and the rate of the catalysed reaction.
What type of graph does the Michaelis-Menten kinetic model create?
Hyperbola curved graph.
How do you measure Vmax and Km?
- Measure initial reaction velocity ,V0, at known substrate concentration and repeat at increasing substrate concentrations
- Then transform the Michaelis-Menten into a straight line equation and plot
- this new graph is then called a Lineweaver-burk plot
What does a high Km value mean?
Enzyme only needs a small amount of substrate to work at half-maximal velocity
What does a low Km value mean?
Enzyme needs a large amount of substrate to work at half-maximal velocity
What are the 4 types of enzyme inhibition?
Reversible competitive, reversible non-competitive, irreversible non-competitive and feedback inhibition.
Describe Reversible competitive inhibition.
binds to active site and blocks substrate access (orthosteric inhibition- same site), doesn’t change the Vmax but Km varies
Describe reversible non-competitive inhibition.
binds to allosteric site and changes the enzyme’s conformation (allosteric inhibition- diff. site), Km stays same but Vmax varies
Describe irreversible non-competitive inhibition
involves formation or breakage of covalent bonds in the enzyme complex
What can control allosteric enzyme activity?
allosteric inhibitors and allosteric activators.
Describe feedback inhibition.
- Final product can inhibit an earlier reaction in the pathway
- form of allosteric control
- These allosteric enzymes that do this do not follow the Michaelis-Menten kinetic model
- Forms a sigmoidal curved graph
What is K1?
The forward rate constant for enzyme association with substrate.
