Enzymes Continued Flashcards
Enzyme inhibitor
A compound that interferes with the catalytic action of an enzyme and so finished the reaction rate
- we can target and inactivate and chosen reaction amongst the thousands of reactions going on in a cells.
- info on active site requirements of specific enzymes
- more general insights on catalytic mechanisms
- have even helped eludicate metabolic pathways
- reversible- competitive, uncompetitive, mixed
- irreversible
Competitive reversible inhibitor
- competed with substrate t hind at the active site on enzyme
- structure resembles that of substrate sufficiently well to allow this
- competitive inhibitor stops substrate from binding, so impedes catalysis from S to P and reduces reaction rate
- due to reversible nature, binding of competitive inhibitor can be overcome by increasing substrate concentration.
- Vmax unaffected by presence of competitive inhibitor
- y intercept unchanged
Uncompetitive reversible inhibitor
- binds at site on enzyme that is distinct from active site
- binding of inhibitor at this distinct site somehow diminishes catalytic activity at active site and reduced reaction rate
- no structural similarity to substrate
- inhibitor binds only to ES complex
- effects of this type of inhibitor cannot be overcome by increasing substrate concentration
- Vmax is reduced
- Km also decreased
- increased Y intercept
Mixed type reversible inhibitor
Mixed inhibited bind at sites on enzyme distinct from active site but can bind to either free enzyme E or the enzyme substrate complex ES
Irreversible enzyme inhibition
- either combine with a functional group on enzyme that is essential for activity, often through covalent modification of active site, sometimes through a particularly stable non- covalent interaction, or they destroy an essential functional group
- rational drug design is the development of new and novel pharmaceuticals- permanent
Regulatory enzyme general activity
Enzymes often work together in groups to carry out all the sequential steps required for an entire metabolic process.
Reaction rates mostly determined by Michaelis- Menten kinetics
- one reaction normally acts as slowest or rate limiting step- enzyme catalysing this is called regulatory enzyme
- linear metabolic pathway- first enzyme usually regulatory
- branched- independent control
Regulatory enzyme
Increase decrease activity in response to other signals
Provide greater degree of finesse in regulation/ control than mere response to S can offer
Required for efficient use of metabolic pathways.
Allow cells and while organisms to respond more effectively to changed conditions at different times
A given metabolic pathway may be regulated by multiple types of regulation
Eg allosteric enzymes
Allosteric enzymes (regulatory)’
Have one or more regulatory sites on their surface in addition to active site
Each site binds to particular metabolite through reversible non covalent interactions
Binding of effector causes conformation change in protein, which is communicated to active site and changes its activity
Effector binding can increase or decrease enzyme activity
More structurally complex - often multimedia proteins (multiple subunits); regulatory and catalytic sites can be on different subunits
International unit of enzyme activity (IU)
The amount of enzyme that catalyses the transformation of 1 micro mole of substrate let minute under specified conditions
Enzyme commission EC
The amount of enzyme that catalyses the transformation of 1 mole of substrate per second
Protein purification
Isolation of a single protein through the physical separation and complete removal of other proteins.
Required for rigorous studies of enzyme activity and behaviour
Determination of amino acid composition
Determination of amino acid sequence
Determination of protein structure
