midterm 2 Flashcards
how to calculate Vmax
1/y int of lineweaver burke
how to calculate km
-1/x int of lineweaver burke
how to calculate Kcat
Vmax/[E]
how is Vmax affected by change in [E]
affected proportionally; e.g. 1/2[E] ==> 1/2Vmax
how is Km affected by change in [E]
it’s not
how is Kcat affected by change in [E]
it’s not
how to calculate efficiency of an enzyme
Kcat/Km
where does a competitive inhibitor bind
the active site
what changes occur during competitive inhibition (km, Vmax, etc)
Vmax does not change; Km increases
where does an uncompetitive inhibitor bind and what does it affect
binds to ES complex without inhibiting substrate binding and inhibits catalytic function only
what changes occur during uncompetitive inhibition (km, Vmax, etc)
decrease in Vmax, decrease in Km, no change in Km/Vmax (slopes are equal)
relate Vmax (+I) to Vmax (-I) for uncompetitive inhibition
Vmax (+I) = Vmax (-I)/alpha’
relate Km (+I) to Km (-I) for uncompetitive inhibition
Km (+I) = Km (-I)/alpha’
where does a mixed inhibitor bind and what does it do
binds enzyme (at regulatory site) with or without substrate and inhibits both substrate binding and catalysis
what changes occur during mixed inhibition (km, Vmax, etc)
decrease in Vmax, increase or decrease in Km
where does a noncompetitive inhibitor bind and what does it do
binds enzyme equally with or without substrate and both inhibits substrate and catalysis
what changes occur during mixed inhibition (km, Vmax, etc)
Vmax decreases, Km stays the same –> same percent inhibition overall; MM curve shifts down and left
Relate Vmax (+I) to Vmax (-I) for a mixed inhibitor
Vmax(+I) = Vmax (-I)/alpha’
relate Km (+I) to Km (-I) for a mixed inhibitor
Km (+I) = (alpha/alpha’)Km (-I)
Relate Vmax (+I) to Vmax (-I) for a noncompetitive inhibitor
Vmax (+I) = Vmax (-I)/alpha’
relate Km (+I) to Km (-I) for a noncompetitive inhibitor
Km (+I) = (alpha/alpha’)Km (-I) …. alpha = alpha’
relate Km (+I) to Km (-I) for a competitive inhibitor
Km (+I) = alphaKm (-I)
calculate alpha
alpha = 1 + [I]/Ki
calculate alpha’
alpha’ = 1 + [I]/Ki’
what does alpha relate to
free enzyme
what does alpha’ relate to
E-S complex
what does Ki and Ki’ tell you
affinity of enzyme to free enzyme and E-S complex, respectively
2 methods to control velocity of enzyme catalyzed rxns
control of enzyme activity and control of amount of enzyme
properties of an efficient enzyme
fast, catalyzing many reactions per second, and be able to accomplish this at a relatively low substrate concentration
what is the michaelis menten equation (linearized and equal to Vo)
1/Vo = Km/(Vmax[S]) + 1/Vmax Vo = (Vmax[S]) / (Km + [S])
what are the 4 assumptions of michaelis menten
- [S]»_space;> [E}
- catalysis is rate limiting: k2 «< k1
- Vo = k2[ES]
- [ES] at steady state: rate of formation = rate of breakdown
what equation/chemical reaction is michaelis menten setup
E + S ES –> E + P
energy charge regulation in anabolic pathways
ATP utilizing ==> activated by ATP, inhibited by ADP/AMP
energy charge regulation in catabolic pathways
ATP regenerating ==> activated by AMP/ADP, inhibited by ATP
What does a decrease in Km tell you about inhibitor affinity (E vs E-S)
higher binding affinity to E-S complex
What does Ki > Ki’ tell you
the inhibitor has a stronger affinity for the E-S complex (dissociation constant for E-S is lower than for free enzyme)
what does a Km increase tell you about inhibitor affinity (Ki)
increase in Km indicates a higher affinity for free enzyme
how can an enzyme with a low kcat be efficient?
have a low Km, so it can bind substrate at relatively low concentrations
