Enzymes

Question 1

Enzymes catalyze reactions by….

Answer 1

increasing chemical reaction rate, reducing free energy needed for reaction to occur, increasing the probability of reaction occurrence

Question 2

Are enzymes bidirectional or unidirectional?

Answer 2

Both

Question 3

Cofactors

Answer 3

Inorganic ions, play a role in stabilizing structures (?)

Cu, Mg, Zn, Fe

Question 4

What is a holoenzyme?

Answer 4

Complete catalytically active enzy,e with coenzymes and cofactors bound

Question 5

What are the six types of enzymes? (slide 4)

Answer 5

oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases,

Question 6

Define Oxidoreductases

Answer 6

.

Question 7

Define Transferases

Answer 7

.

Question 8

Define hydrolases

Answer 8

.

Question 9

Define lyases

Answer 9

.

Question 10

Define Isomerases

Answer 10

.

Question 11

Define Ligases

Answer 11

.

Question 12

How does the structure of the enzyme relate to its substrate’s structure?

Answer 12

the enzyme matches the substrate’s transition state structure (enzyme is complementary to transition state)

Question 13

What are the four activation barriers that enzymes overcome?

Answer 13

entropy of molecules in a solution, solvation shell, substrate conformation, and substrate orientations

Question 14

Define kinetics

Answer 14

the rate at which enzymes create products

kinetics allow:

• identification of mechanism
• rate limiting steps of product formation
• identification of inhibitors

Question 15

Define velocity

Answer 15

the primary measure of reaction rate

• initial velocity (Vo)
• maximum velocity (Vmax)

Question 16

Define Km (slide 9/10)

Answer 16

the concentration at which the Vo is half of the Vmax

or the substrate concentration at which the enzyme is functioning at half capacity (?)

Question 17

Define Km (slide 9/10)

Answer 17

the concentration at which the Vo is half of the Vmax

or the substrate concentration at which the enzyme is functioning at half capacity (?)

Question 18

What affects velocity

Answer 18

enzyme, substrate, cofactors, coenzymes, enzyme modifications, pH, temperature

Question 19

How do drugs/inhibitors relate to Km?

Answer 19

drugs want to move it to the left (reach half max sooner/enzyme is more efficient at becoming active)

if you move it to the right (….)

Question 20

How do drugs/inhibitors relate to Vmax?

Answer 20

you can move the Vmax to increase or decrease ….?

Question 21

What are the two classes of inhibitors?

Answer 21

Irreversible and reversible inhibitors

Question 22

Irreversible inhibitors

Answer 22

inhibitor covalently binds to enzyme –> preventing fx and leading to degradation
-suicide

(permanent, bind enzyme and need to be replaced)

Question 23

Reversible inhibitors

Answer 23

inhibitor binds the enzyme or substrate to temporarily affect catalysis

• competitve
• mixed
• uncompetitive
• noncompetitive

Question 24

what are the four types of reversible inhibitors

Answer 24

competitive, uncompetitive, mixed, noncompetitive

Question 25

competitive inhibition

Answer 25

inhibitor competes with substrate

Km moves to the right, but no change in Vmax
—preventing substrate from binding/would need to increase amount of substrate to make up for this

Question 26

uncompetitive inhibition

Answer 26

inhibitor binds the ES (enzyme-substrate) complex, but not the enzyme alone

Reduces Vmax, Km moves left
—total amount of product that can be produced is impaired (prevention of conversion from substrate to product)

Question 27

mixed inhibition

Answer 27

inhibitor binds enzyme alone or ES complex
-affects substrate binding and enzyme

Reduces Vmax, Km moves right
—prevents substrate binding and prevents substrate to product

Question 28

noncompetitive inhibition

Answer 28

• inhibitor binds the enzyme or ES complex
• slows or stops enzymatic process, substrate binding not affected

Reduces Vmax, no change in Km
—inhibitor just prevents substrate to product

Question 29

Allosteric regulation

Answer 29

Allosteric Enzymes:

• enzyme conformation is changed by effector binding
• this can alter catalytic fx (stimulate/inhibit)
• do not follow Michaelis-Menten Kinetics
• complex protein structures

Question 30

What are the types of allosteric/covalent modifications?

Answer 30

phosphorylation, acetylation, methylation, ubiquitination, and myristoylation

Question 31

What is homotropic regulation

Answer 31

the substrate itself regulates enzyme fx

regulation occurs at separate site from substrate binding

Question 32

what is heterotropic regulation

Answer 32

non-substrate molecules regulate enzyme fx

regulation occurs at separate site from substrate binding