Enzyme Kinetics Flashcards
What is enzyme kinetics?
The study of rates of chemical reactions catalyzed by enzymes E+S-->ES-->E+P - E=enzyme - S=substrate - P=product
What is the relationship between ES formed and E+S consumed in a steady state?
They are equal
Consuming all substrate results in free _____ and free _____
enzymes/products
What does V0 represent?
initial velocity (initial rate of reaction)
What does Vmax represent?
maximum velocity (reaction reaching plateau/saturation)
What does Km represent?
Michaelis-Menten constant, substrate concentration at 1/2 Vmax in mol
What is the Michaelis-Menten equation?
V0=(Vmax[S])/(Km+[S])
Km = ___ when V0 = ___
[S] / (1/2)Vmax
What type of graph can be used to determine the variables of the M-M equation?
a V0 vs. [S] graph
____ = rate of product production, = ___ in Km=([K2]+[K-1])/(K1)
Kcat / [K2]
K1=___–>___ rate, K2=___–>___ rate, K-1=___
E+S/ES/ES/E+P/E+S/ES
Enzyme eficiency constant = ?
= Kcat/Km
Kinetic _____ is the order of binding __ and releasing __, enzyme _____ allows distinguishing between kinetic ____ the more than one _____ is involved
mechanism/S/P/kinetics/mechanism/substrate
What are Lineweaver-Burk plots? What are the axis labels? What do the intercepts represent?
Linearized double-reciprocal plots for analyzing two substrate data or inhibition
- plots 1/V0 vs 1/[S]
- x-intercept=1/Km
- y-intercept=1/Vmax
What are the types of kinetic mechanisms and how would you identify them on a L-B plot?
1) Sequential Kinetic Mechanism
a. Ordered: will show lines intersecting NOT on the y-axis
b. Random: will down lines intersecting at the y-axis
2) Ping Pong Kinetic Mechanism: shows parallel lines
What is enzyme inhibition and what are the types?
It is when enzyme activity is decreased by inhibitors
1) competitive
2) uncompetitive
3) mixed
What is competitive inhibition and its characteristics?
Inhibitor binds to active site in competition with the substrate
- Vmax: no change
- Km: increase
- L-B plot lines: intersect at y-axis
- catalysis: unaffected
What is uncompetitive inhibition and its characteristics?
Inhibitor binds to ES complex to inhibit substrate from binding
- Vmax: decrease
- Km: decrease
- L-B plot lines: parallel
- catalysis: inhibited
What is mixed inhibition and its characteristics?
Inhibitor binds to regulatory site to inhibit substrate from binding
- Vmax: decreases
- Km: changed
- L-B plot lines: intersect left of y-axis
- catalysis: inhibited
Which type of inhibitors permanently shut down the enzyme?
Irreversible inhibitors
Which type of inhibitors can bind and dissociate from free enzymes or the ES complex?
Reversible inhibitors
What are the types of enzyme regulators and their functions?
1) non-covalent/allosteric regulators: small chemicals that bind to the allosteric site and can improve or reduce enzyme function
2) covalent modification: either reversible or irreversible
a. reversible: uses signalling pathways to regulate PRO activity, can enter and exit
b. irreversible: activate zymogens/proenzymes (can be converted into enzymes when activated)
