Enzyme Mechanisms Flashcards
Cofactors
Are inorganic and organic molecules that help an enzyme catalyse a reaction
Coenzymes
Non protein organic molecules that bind an apoenzymes to proteins to produce an active holoenzyme eg NADH
Apoenzymes
Enzymes that are lacking their necessary cofactors for proper functioning , the binding of an enzyme to its cofactor from a hole
What are metalloenzymes
Enzyme tgat cannot function without metal ions in the active site
What is the Michaelis menten equation
Used to model the rate an a enzymatic reaction occurs
Allows you to predict how fast a reaction may take based or conc of reactants
Can determine how much substrate needs to be present before it gets converted into biologically relevant quantities
What two assumptions must be made about the mm equation
[s]»_space;> [E]
Assumed tgat the system is in a steady state. Ie the ES complex is formed at the same rate that it is being broken down so that overall [ES] is constant.
K1[E][s] = k-1 [ES] + k2 [ES]
MM equation
Notes
What is Km an indicator of
The affinity that an enzyme has for a given substrate , and hence the stability of the enzyme substrate complex
What do small Km values mean
Tight binding
What do high km values mean
Weak binding.
Turnover number
Kcat
The maximum no of substrate molecules converted to product per enzyme per unit of time
Kcat=vmax/Et
Catalytic efficiency
Shows what the enzyme can accomplish when abundant enzyme sites are available
Kcat/Km
Allows direct comparison of an enzyme towards different substrates
What is an enzyme inhibitor
An enzyme inhibitor is a molecule that binds to an enzyme and decreases its activity
Types of enzyme inhibitors
Reversible inhibitors - attach to enzymes with non covalent bonds such as hydrogen bonding , hydrophobic interactions , ionic bonds
Irreversible inhibitors - covalently modify an enzyme and inhibition therefore cannot be reversed
Types of reversible enzyme inhibitors
Competitive inhibitors - the substrate and inhibitor cannot bind to the enzyme at the same time . This usually results from the inhibitor having an affinity for the active site of an enzyme where the substrate also binds. Vmax remains the same as the enzyme is not modified but Km will increase as some active sites are occupied so will take longer to reach half of v max
Non competitive inhibitors - the binding of the inhibitor to the enzyme will reduce its activity but not affect the binding of the substrate. V max will decrease due to the inability of the traction to proceed as efficiently , but Km will remain in the same as actual binding of the substate will still function properly
Mixed inhibition - the inhibitor can bind to the enzyme at the same time as the enzymes substate . However , binding of the inhibitor affects binding of the substate and vice versa. Causes vmax and Km to change
Uncompetitive inhibitors - the inhibitor will bind only to the es complex . This causes vmax and Km to change.
