Enzyme - Factors Affecting Activity Flashcards
What can enzyme activity be affected by in vitro?
Inhibitors
Physical Factors
Cellular Regulation
Temperature
What may temperature increase lea dto?
Thermal denaturation of weak bonds stabilising protein conformation with protein optimum
How does pH affect enzyme activity?
Electrostatic interactions of enzyme and substrate by ionisation
What is the average enzyme optimum?
5-8
What are the pH optimum of digestive and intestinal enzymes?
2 and 8
What concentrations regulate enzyme activity?
Substrate and Product
When might product inhibition occur?
The more the substrate hte more the product
What does product inhibition affect?
Overall measured rates of reactions and not enzyme catalytic properties
Feedback Inhibition
This is the phenomenon by which the final metabolite of a pathway inhibits the synthesis of an enzyme, usually the first one
What is an example of feedback inihbition?
Rate-limiting step where final product of the pathway behave as an inhibitor for it
What is an example of feedback inhibition?
3-phosphoglycerate dehydrogenase
phosphoglycerate dehydrogenase
This is the first commited enzyme in the serine synthesis pathway
What is the structure of 3-PGD
Tetramer of 4 identical subunits with 4 catalytic site and 4 regulatory serine-binding sites
Allosteric Regulation
This is where protein functional activity is altered by the binding of an effector at an allosteric site that is topograhpically distinct from the active site
What is allosteric regulation associated with often?
Multi-subunit enzymes with positive and negative regulators
Co-operative Binding
THis occurs if the number of binding sites of a macromolecules that are occupied by specific type of ligand is a nonlinear function of the ligands concentration
How does allosteric regulation relate to MMK?
S is sigmoidal as substrate binding to one site decreases the Km at other active sites resulting in rapid response to increased S
What is the sigmoidal allosteric plot related to?
T state and R state of their enzymatic activity
What does switch from T to R do>?
Decrease Km and increase reaction rate
What is an example of allosteric regulation?
Aspartate Carbamoyltransferase
Aspartate Carbamoyltransferase
This is a transaminase enzyme catalysing conversion of aspartate and alpha-ketoglutarate to oxaloacetate tand glutamate
Where is ACT used?
First commited step in pyrimidine synthesis where endpoints are cytidine triphosphate
What does cytidine triphosphate transform ACT to?
From a relaxed state to Tense state
What is ACTase activity inhbiited by?
Presence of CTP
Iso\ymes
These are alternative forms of the same enzyme activity existing in different proportions in different tissue
What does the different enzymatic activity of isozymes mean?
Different Km and Vmax
What are isozymes encoded by?
Gene families
What is an example of isozymes?
LDH conversion of lactate to pyruvate
What are the two forms of LDH?
H Form
M Form
H Form
This is found in the heart with higher affinity, can be inhibited by pyruvate with optimization to conversion of lactate to pyruvate for aerobic
M Form
This is found in skeletal muscles with faster catalysis, optimised to pyruvate to lactate conversion in glycolysis
