Introduction to enzyme kinetics

Question 1

What is an enzyme assay?
What is it useful for?

Answer 1

-A test to determine the presence of an enzyme by its activity
-useful for monitoring enzyme activity and detecting enzyme levels.

Question 2

Enzymes produce very high yields of______

Answer 2

products

Question 3

Name some ways to determine the presence of an enzyme by it’s activity

Answer 3

-Useful for monitoring enzyme activity (e.g. during purification).
-Useful for detecting levels of enzyme (e.g. diagnostic testing).

Question 3

Why are assays performed under different conditions?

Answer 3

-provides starting point for understanding how enzymes achieve the incredible acceleration of the rate at which the substrate is converted to a different molecule

Question 4

What is the Michaelis-Menten equation?

Answer 4

A mathematical description of enzyme kinetics that relates the reaction velocity to substrate concentration.

Question 5

What main characteristic do enzymes possess regarding substrate recognition?

Answer 5

Enzymes have a high degree of specificity and can selectively recognize their substrate.

Question 6

What is kcat?

Answer 6

The turnover number, representing how fast an enzyme can convert substrate to product when saturated with substrate.

Question 7

What does the term “Vmax” refer to in enzymatic reactions?

Answer 7

Vmax is the maximum initial rate (velocity) of a reaction.

Question 8

What has to occur for Vmax to be reached?

Answer 8

substrate needs to be in excess

Question 9

What helps to find the mechanisms of a chemical reaction?

Answer 9

Kinetic analysis

Question 10

Define enzyme activity

Answer 10

the ability of an enzyme to promote a particular chemical reaction

Question 11

Why is enzyme activity measured indirectly?

Answer 11

because it is an experimental value and strictly dependent on the conditions of the reaction

Question 12

What is the induced fit model of enzyme action?

Answer 12

indicates that the enzyme changes shape to accommodate the substrate.

Question 13

Specific Activity=

Answer 13

Activity Enzyme/ Mass of Total Protein

Question 14

Vo is the

Answer 14

initial rate of the reaction
(rate of product produced per time)

Question 15

At later stages, the reaction can be negatively affected by:

Answer 15

-product accumulation (inhibition effect).
-Substrate depletion
-Enzyme can get compromised

Question 16

Why is the ratio kcat/KM important?

Answer 16

It is a measure of catalytic efficiency and helps compare different enzymes under conditions of low substrate concentration.

Question 17

Describe the “Lock and Key” mechanism in enzyme action.

Answer 17

The “Lock and Key” mechanism describes how enzymes are specifically shaped to fit their substrate, analogous to a key fitting into a lock.

Question 18

Define Enzyme saturation

Answer 18

The point at which all active sites of enzymes are occupied by substrate, reaching maximum velocity (Vmax).

Question 19

What is the relationship between substrate concentration ([S]) and reaction velocity (v) according to the Michaelis-Menten equation?

Answer 19

v = Vmax [S] / (KM + [S]).

Question 20

How does enzyme concentration affect reaction rate?

Answer 20

The reaction rate is proportional to enzyme concentration when substrate concentration is constant

Question 21

Kcat and Km are characteristic properties of______

Answer 21

a given enzyme at a particular PH and temperature

Question 22

What is the turnover number (kcat)?

Answer 22

It indicates how many substrate molecules one enzyme can convert to product per unit time when saturated with substrate

Question 23

How does enzyme specificity relate to its function?

Answer 23

Enzymes exhibit a high degree of specificity, recognizing and binding only certain substrates

Question 24

What is the significance of the catalytic efficiency ratio kcat/KM?

Answer 24

It provides insight into how effectively an enzyme converts substrate to product, especially at low substrate concentrations.

Question 25

What is the impact of product accumulation on enzyme activity?

Answer 25

Product accumulation can inhibit enzyme activity, leading to decreased reaction rates over time

Question 26

What is the relationship between enzyme activity and total protein concentration?

Answer 26

Specific activity is calculated as enzyme activity (units) divided by total protein concentration (mg).

Question 27

How does the Michaelis-Menten equation describe enzyme kinetics?

Answer 27

It models the rate of enzymatic reactions as v= KM+[S] Vmax[S] ​

Question 28

What does a high KM value suggest about substrate binding?

Answer 28

A high KM indicates weak binding affinity; more substrate is needed to reach half of Vmax

Question 29

Explain the concept of enzyme saturation

Answer 29

Enzyme saturation occurs when all active sites of the enzyme are occupied by substrate, leading to a maximum reaction rate.

Question 30

What is the role of inhibitors in enzyme kinetics?

Answer 30

Inhibitors can decrease enzyme activity by binding to the enzyme or enzyme-substrate complex, affecting reaction rates.

Question 31

How can enzyme kinetics be applied in clinical diagnostics?

Answer 31

Enzyme assays can monitor enzyme levels and activity to diagnose conditions like heart attacks or diabetes.

Question 32

What is the effect of temperature on enzyme kinetics?

Answer 32

Each enzyme has an optimal temperature range; deviations can lead to decreased activity or denaturation.

Question 33

What is the significance of enzyme purification?

Answer 33

Purification increases the specific activity of an enzyme, allowing for better characterization and study.

Question 34

How do competitive inhibitors affect the Michaelis-Menten equation?

Answer 34

Competitive inhibitors increase KM without affecting Vmax, as they compete with substrate for the active site

Question 35

What is the diffusion limit in enzyme kinetics?

Answer 35

It is the upper limit for kcat/KM, representing the maximum efficiency of an enzyme under ideal conditions