Enzymes 3 Flashcards
(22 cards)
Why Lineweaver-Burke is used
It shifts in quite noticeable ways when an inhibitor is introduced to an enzyme
Which point of a metabolic pathway is the most efficient point of control
The rate limiting step
Regulatory Mechanisms used for Enzyme Regulation
- Allosteric Activation/Inhibition (Fastest)
- Phosphorelation/Covalent Modification
- Protein-Protein Interactions
- Proteolytic Cleavage
Allosteric Modulation/Inhibition
Activity Modulation via reversible, non-covalent binding of small molecules (effectors) at a non-active site
Positive Effector vs Negative Effector
Positive - Allosteric Activator
Negative - Allosteric Inhibitor
How do allosteric effectors affect S0.5 and Vmax
Can affect S0.5 and/or Vmax
Homotropic Effector
A substrate that serves as an allosteric effector
**THINK HAEMOGLOBIN AND R/T STATES
Heterotropic Effector
An effector that is different to the substrate - e.g. end product inhibition (citrate to phosphofructokinase)
Co-operativity
When a substrate binds to one subunit, it enhances/reduces the catalytic properties of other subunits
(Positive or Negative Co-operativity)
Which type of Effector is more commonly seen in Co-operativity
(homo or hetero tropic)
Homotropic Effectors
The Concerted Model
The first substrate molecule struggles to bind as all subunits are in the Tense state, but once it binds, all adjacent subunits along with the bound subunit go into the Relaxed state
The Sequential Model
Each subunit only affects one other subunit
Examples of Allosteric Regulation
Glycolysis (Phosphofructokinase) TCA Cycle (Isocitrate Dehydrogenase)
Covalent Modification
Sticking functional groups onto a protein (e.g. phosphorelation)
Protein Kinases
An enzyme that phosphorelates a molecule
They use ATP as a phosphate donor
Protein Phosphatase
Enzymes that remove phosphate groups via hydrolysis
How can enzymes change from Tense to Relaxed form
The binding of a positive allosteric effector or phosphorelation
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Example of Protein-Protein interactions to regulate enzymes
Calcium-Calmodulin family of modulator proteins
Proteolytic Cleavage
The process of breaking the peptide bonds between amino acids in proteins which irreversibly activates or inactivates enzymes
How can proteolytic cleavage occur
Enzymes by intracellular proteases on lysosomes or proteasomes
