Enzyme Kinetics

Question 1

What is enzyme kinetics?

Answer 1

The study of rates of chemical reactions catalyzed by enzymes
E+S-->ES-->E+P
- E=enzyme
- S=substrate
- P=product

Question 2

What is the relationship between ES formed and E+S consumed in a steady state?

Answer 2

They are equal

Question 3

Consuming all substrate results in free _____ and free _____

Answer 3

enzymes/products

Question 4

What does V0 represent?

Answer 4

initial velocity (initial rate of reaction)

Question 5

What does Vmax represent?

Answer 5

maximum velocity (reaction reaching plateau/saturation)

Question 6

What does Km represent?

Answer 6

Michaelis-Menten constant, substrate concentration at 1/2 Vmax in mol

Question 7

What is the Michaelis-Menten equation?

Answer 7

V0=(Vmax[S])/(Km+[S])

Question 8

Km = ___ when V0 = ___

Answer 8

[S] / (1/2)Vmax

Question 9

What type of graph can be used to determine the variables of the M-M equation?

Answer 9

a V0 vs. [S] graph

Question 10

____ = rate of product production, = ___ in Km=([K2]+[K-1])/(K1)

Answer 10

Kcat / [K2]

Question 11

K1=___–>___ rate, K2=___–>___ rate, K-1=___

Answer 11

E+S/ES/ES/E+P/E+S/ES

Question 12

Enzyme eficiency constant = ?

Answer 12

= Kcat/Km

Question 13

Kinetic _____ is the order of binding __ and releasing __, enzyme _____ allows distinguishing between kinetic ____ the more than one _____ is involved

Answer 13

mechanism/S/P/kinetics/mechanism/substrate

Question 14

What are Lineweaver-Burk plots? What are the axis labels? What do the intercepts represent?

Answer 14

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

Question 15

What are the types of kinetic mechanisms and how would you identify them on a L-B plot?

Answer 15

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

Question 16

What is enzyme inhibition and what are the types?

Answer 16

It is when enzyme activity is decreased by inhibitors

1) competitive
2) uncompetitive
3) mixed

Question 17

What is competitive inhibition and its characteristics?

Answer 17

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

Question 18

What is uncompetitive inhibition and its characteristics?

Answer 18

Inhibitor binds to ES complex to inhibit substrate from binding

• Vmax: decrease
• Km: decrease
• L-B plot lines: parallel
• catalysis: inhibited

Question 19

What is mixed inhibition and its characteristics?

Answer 19

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

Question 20

Which type of inhibitors permanently shut down the enzyme?

Answer 20

Irreversible inhibitors

Question 21

Which type of inhibitors can bind and dissociate from free enzymes or the ES complex?

Answer 21

Reversible inhibitors

Question 22

What are the types of enzyme regulators and their functions?

Answer 22

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)