Practical D Flashcards
Active site contains ______ groups when pH range is broad
Uncharged reactive groups
Active site contains ______ groups when pH range is narrow
Charged reactive groups
Why do enzymes have pH optima different from cellular average?
Subcellular compartmentation
Why are results for enzyme activity falsely low if incubation time is too long?
Rate of product formation slows as incubation time increases. Enzymes may lose significant amount of activity during incubation.
Why are some enzymes unstable in dilute solution and how is this overcome?
Some form dimers or other aggregates in natural form and disaggregate in dilute solutions. This is overcome by addition of large amounts of inert protein.
If working with unpurified preparation or unknown mr of enzyme then expressed as
Mol of product formed/ unit time/ value of preparation (gram of original tissue / unit time as the total amount of original tissue)
If partially purified enzyme, specific activity =
mol of product formed/ unit time/ mg protein
If enzyme is pure then ______ can be determined as
Rcat (catalytic rate constant) = mol of product formed/ sec/ mol of enzyme
Line-weaver burk plot is a
Double reciprocal plot where y int = 1/vmax + x int = -1/Km
Irreversible inhibitors are useful for which type of drugs?
Useful for drugs that need to be taken only every few days -> covalent modification of the enzyme so activity is permanently reduced
Inhibitor constant
indication of how potent an inhibitor is: conc. required to produce half max. Inhibition
How can we tell if inhibitor is competitive in a Dixon plot?
1/v agonist inhibitor conc. at each conc. of substrate (Dixon Plot) gives a formula of intersecting lines
-> If competitive, lines converge above x axis and value for [I] when they intersect = Ki
