Enzymes III BI25M7 Flashcards
What does the concerted model explain about allosteric activators?
Allosteric activators will stabilize the ‘open’ conformation allowing S to bind more effectively
The concerted model describes how allosteric enzymes change their conformation upon substrate binding.
What is the effect of allosteric inhibitors on enzyme conformation?
Allosteric inhibitors will stabilize the ‘closed’ conformation, making it difficult for S to bind effectively
This mechanism reduces the enzyme’s activity by preventing substrate binding.
What characterizes irreversible inhibitors?
They bind to the enzyme in a covalent and irreversible way
This type of inhibition permanently deactivates the enzyme.
How does cyanide (CN-) affect cytochrome c oxidase?
CN- binds to Fe3+ of cytochrome c oxidase and disrupts the terminal respiratory system
This blockage leads to a lack of ATP production in cells.
What is the effect of non-competitive inhibitors on Vmax and Km?
Vmax decreases while Km remains unchanged
Non-competitive inhibitors affect the overall rate of reaction without affecting substrate binding affinity.
What are catalytic antibodies?
Antibodies generated against biological molecules that can mimic enzyme active sites
They can facilitate reactions similar to enzymes.
What is a transition state analogue?
An inhibitor that mimics the transition state of a reaction
Oseltamivir (Tamiflu) is an example, blocking neuraminidase activity.
What is the mechanism of action of AZT in HIV treatment?
AZT acts by competitive inhibition of reverse transcriptase
This enzyme is crucial for converting ssRNA to dsDNA in HIV.
What happens to Km and Vmax when competitive inhibitors are present?
Km increases while Vmax remains unchanged
This indicates a decrease in affinity for the substrate due to competition.
What are the two main ways regulatory enzymes modulate reactions?
Allosteric control and covalent modification
These mechanisms regulate enzyme activity in metabolic pathways.
What is feedback inhibition?
A process where the end product of a pathway inhibits an upstream enzyme
This regulates the metabolic pathway based on product levels.
What is the role of allosteric effectors?
They bind non-covalently to enzymes, changing their structure and function
This can either activate or inhibit enzyme activity.
What does the sequential model of enzyme action assume?
Sub-units exist in a conformation that can bind S, activators, or inhibitors
Binding causes conformational changes that enhance substrate binding.
What is phosphorylation in the context of enzyme regulation?
A reversible covalent modification that can activate or deactivate enzymes
Protein kinases add phosphoryl groups, while phosphatases remove them.
What are proproteins?
Inactive precursor proteins that can be activated by proteolytic cleavage
Digestive enzymes are examples of this regulation.
How do enzymes function as catalysts?
They increase reaction rates by lowering activation energy barriers
Enzymes have specific active sites for substrate binding.
What are the two models that explain allosteric enzyme kinetics?
Concerted model and sequential model
Both models describe how enzyme sub-units cooperate in function.
What type of curve do most enzymes show when plotting V0 against [S]?
Hyperbolic curve
This reflects the relationship between enzyme activity and substrate concentration.
