Enzymes Flashcards
How do enzymes specify a chemical reaction?
- Site of occurrence - location (intracellular/extracellular)
- Rate of reaction - amount of active enzyme present
- Reaction time - state (active/inactive)
What are the 2 enzymes responsible for synthesis and degradation of acetylcholine?
ChAT: for synthesis (acetyl CoA +Choline -> Ach + CoA)
AChE: for degradation (Ach + H2O -> Choline + acetic acid)
Sites present on an enzyme
- Active site - binding of substrate
- Binding site - for coenzyme/cofactor
- Regulatory site - for activator/inhibitor
- Catalytic site - provide chemical environment
2 ways for an enzyme to function as a catalyst
- Provide alternative pathway with lower activation energy
- Mechanical straining of molecule in catalytic site
- > change shape to facilitate change of structure
- > accounts for the specificity of enzyme
Ways of changing accessibility of enzyme
Introduce small structural changes
1. Phosphorylation - fast, reversible
2. Cleavage of peptide bond - fast, irreversible
3. Activating/Inactivating enzyme - by activator/inhibitor
Adjust total amount of enzyme
4. Change rate of synthesis and degradation - slow, irreversible (long-term regulation)`
What is positive influence? When does it occur? What curve would it demonstrate on graph?
Occurs on oligomeric enzyme with multiple subunits
- > bound subunit can exert positive influence on neighbouring subunits to increase the affinity of substrate
- Sigmoidal curve*
What do allosteric regulators do?
+ allosteric regulators:
put oligomeric enzyme in active site -> demonstrate more sigmoidal curve
- allosteric regulators:
less sigmoidal curve, lengthens initial phase