Enzyme Kinetics

Question 1

What is the simple model mechanism (pathway) used to examine enzyme kinetics?

Answer 1

A single substrate and product, with no inhibiters.
Where:
E represents the enzyme
S represents the substrate
ES = substrate-enzyme complex
P= product

Question 2

What is the steady state?

Answer 2

concentration of enzyme-substarte complex remains relatively constant. Occurs because the rate of ES formation equals the rate of its breakdown

Question 3

What is the km?

Answer 3

Michaelis Constant. It represents the substrate concentration at which the reaction velocity is half of Vmax. It is an approximate measure of the substrate’s binding affinity for the enzyme. higher km= weaker binding affinity
lower km= stronger binding affinity

Question 4

What is kcat?

Answer 4

Turnover number
-reflects catalytic efficiency of enzyme
- how much substrate molecules are converted to product /enzyme moelcule/second when the zyme is saturated with substrate

Question 5

How is the Michaelis-Menten equation related to the fraction of sites bound by a ligand?

Answer 5

there is a mathematical similarity. It highlights the connection between substrate binding and enzyme activity. If V0 / Vmax, then [S]/km + [S].
suggesting Km is analogous to Kf, and relfects the enzyme’s affinity for the substrate. Both Km and Kd represent the concentartion of a molcule at which half of the binding sites are occupied

Question 6

What happens to the equation when there is very low [S]? Very high [S]? Is this consistent
with the kinetic curve, and why

Answer 6

very low [S]«Km
simplified to V0 = Vmax/Km. Reaction velocity is directly proportional to [S]

Very high [S]» Km simplifies to V0= Vmax. reaction becomes independent of [S] and reaches its maximum rate.

This is consistent with the typical hyperbolic kinetic curve for enzymes, where the initial velocity increases rapidly at low [S] and plateaus at high [S]

Question 7

What is the enzyme specificity constant?

Answer 7

Kcat/Km It measures the catalytic efficiency of an enzyme. It represents how efficiently an enzyme converts a substrate into product

Question 8

What does a high enzyme specificity value indicate?

Answer 8

It indicates high enzyme efficiency. Max value is limited by rate of diffusion of the substrate to the enzyme’s active site.

Question 9

How is the equation for a Lineweaver-Burk plot determined?

Answer 9

obtained by taking the reciprocal of both sides of the Michaelis-Menten equation and rearranging the terms

Question 10

What are the benefits of a Lineweaver-Burk plot with respect to determining kinetic
parameters of an enzyme?

Answer 10

linearizes the Michaelis-Menten relationship, allowing for easier determination of kinetic parameters such as Km and Vmax. It is particularly useful for analyzing:
○Two-substrate data
○Enzyme inhibition patterns

Question 11

What is the slope of Lineweaver-Burk Plot?

Answer 11

Km/Vmax

Question 12

What is the y axis of Lineweaver-Burk Plot?

Answer 12

1/V0

Question 13

What is the x axis of the Lineweaver-Burk Plot?

Answer 13

=1/[S]

Question 14

What is the y-intercept of Lineweaver-Burk Plot?

Answer 14

1/Vmax

Question 15

What is the X-intercept of Lineweaver-Burk Plot?

Answer 15

-1/Km

Question 16

What is the sequential mechanism?

Answer 16

Both substrates must bind to the enzyme to form a ternary complex before the reaction can proceed. This can occur in a random or rodered manner

Question 17

What is the ping-pong mechanism?

Answer 17

one subtrate binds and reacts, modifying the enzume. The first product is released before the second substrate binds and reacts

Question 18

What can a Lineweaver-burk plot tell us about 2 substrate?

Answer 18

This helps distinguish between sequential and ping-pong mechanism.