Enzymes Flashcards
Ribozymes?
- Catalytic RNA molecules
- No protein component
Cofactor?
Non protein component required for activity
Co enzyme?
Enzyme produced from a vitamin such as FAD or NAD
Prosthethic group?
Covalently bound (or very closely associated) cofactor
Apoenzyme?
Inactive enzyme that is activated when cofactor binds
Holoenzyme?
The whole enzyme
Why isn’t a spontaneous reaction instant?
Needs an activation energy
What is the transition state?
- The instantaneous moment new chemical bonds are formed and old are broken
- From this point the reaction can go back to reactants or become products
What type of bonds occur between substrate and enzyme
Non covalent
What is the active site complementary to?
Transition state
In what 3 ways do enzymes reduce activation energy?
- Reduce entropy
- Desolvation
- Induced fit
How does reducing entropy reduce the activation energy?
Increases chance that substrates collide in the proper orientation
How does desolvation lower activation energy?
H bonds with substrate/solution replaced by H bonds with substrate/enzyme
What is the michaelis-menton equation?
E + S ES —-> P
In the reversible step, which reaction is slower?
Reforming the products
What is Km?
The substrate conc. when the reaction v is half the maximum
What does Km measure?
The ratio of formation of ES from E + S, compared to the formation of E + S from ES
What does Km show you?
The affinity of the enzyme for the substrate
What does a large Km tell you?
- ES complex is unstable therefore
- More ES —-> E + S
What does glucokinase catalyse?
Glucose + ATP to G-6-P
What does an elevated level of creatine kinase allow you to diagnose?
- MI
- Infection
What are the 2 reaction mechanisms that an enzyme catalysed reaction with 2 substrates can follow?
- Random w/ ternary complex
- Ordered w/ ternary complex
- No ternary complex
What is random with a ternary?
- Either substrate can bind first
- Forms two products
Ordered ternary reaction?
- One substrate attaches first, the other follows
- Forms one product
What is the mechanism of reaction when no ternary complex forms?
- 2 reactions occurs
- 1st reaction with 1st substrate alters the enzyme and produces a product
- Altered enzyme can now bind to 2nd substrate and produces a second product
What type of reactions have no ternary complex formation
Transamination
How does pH alter enzyme function
pH will change the charge of amino acids in the sequence and can make the active set stop functioning
Effect of a competitive inhibitor on Vmax and Km?
- Vmax same
- Km decreases
Effect of a non competitive inhibitor on Vmax and Km
- Vmax decreases
- Km same
