10. Enzymes Flashcards
Compounds, usually organic in nature, required by some enzymes before they will catalyze reactions
Coenzyme
A non-protein molecule, organic or inorganic that may be needed for enzyme function
Are ions that induce the necessary configuration for proper binding to the substrate
Cofactor
3 defining characteristics of enzymes
- Not consumed or permanently altered during the rxn
- Only small amounts required b/c re-used
- Accelerate speed at which a chemical rxn reaches equilibrium, but doesn’t alter equilibrium constant
What is an isoenzyme
Enzymes that catalyze the same rxn but have different structural and biochemical properties
2 of the most common isoenzymes
- Creatine kinase (CK)
- Lactate dehydrogenase (LD)
An organic cofactor bound tightly (covalently and permanently) to the apoenzyme
Prosthetic group
What is an apoenzyme
Heat-labile protein of the enzyme which requires a coenzyme for full catalytic activity
Class of enzyme:
Transfer of functional groups (other than hydrogen) between 2 substrates
Transferases
Class of enzymes:
Oxidation-reduction between 2 substrates
Oxidoreductases
These catalyze the hydrolytic (addition of water) cleavage of compounds
Hydrolases
Removal of groups from substrates without hydrolysis, to form double bonds
Lyases
Joining of 2 molecules coupled with hydrolysis of a pyrophosphate bond in ATP
Ligases
Define catalyst
A substance that accelerates the rate of a chemical rxn without becoming modified itself
Inorganic cofactors include metallic and non-metallic ions
May be essential for reaction or may just enhance the reaction rate
Activators
AKA complex enzyme (apoenzyme and cofactor/coenzyme)
Holoenzyme
Example of a hydrolase
Amylase
What enzyme classification is LD
Oxidoreductase
What is an International Unit
Amount of enzyme that will catalyze the reaction of 1 umol of substrate per minute
In a rxn catalyzed by an enzyme, the enzyme binds to the ______ state better than the _______ state
TRANSITION state better than the GROUND state
Temperature equilibration and mixing of reagents occur in this phase
Lag phase
Which order kinetics
- Increasing rate of rxn
- Changing rate of rxn
First order kinetics
Reaction rate is constant with time
Zero order phase
3 factors affecting enzyme levels in plasma or serum
- leakge of enzymes from cells
- damage to cell membrane
- clearance of enzymes
Competitive inhibition Km, Vmax
Km INCREASE
Vmax no change
Noncompetitive inhibition Km, Vmax
Km no change
Vmax DECREASES
Uncompetitive inhibition Km, Vmax
BOTH decrease
