Enzymes

Question 1

Enzyme

Answer 1

protein catalyst offering control in biological processes

Question 2

4 Enzymatic malfunctions

Answer 2

Gout
Porphyria
Type 1 albinism
Haemophilia A

Question 3

HIV 1 protease inhibitors

Answer 3

Target for AIDS therapy with drugs: 
Indinavir
Saquinavir
Ritonavir
Nelfinavir

Question 4

Binding of enzyme to substrate provides:

Answer 4

Transition state

Question 5

Enzyme-Substrate binding models

Answer 5

Lock - Key

Induced Fit

Question 6

DNA topoisomerase inhibitors

Answer 6

Anticancers

Question 7

Angiotensin converting enzyme inhibitors

Answer 7

Blood pressure

Question 8

Xanthine oxidase inhibitors

Answer 8

Gout

Question 9

HIV proteinase inhibitors

Answer 9

Antiviral

Question 10

Catalase reaction

Answer 10

2 H2O2 2 H2O + O2

Question 11

Kinetic Experiments

Answer 11

[S]
[P]
size - DNA restriction nucleases
colour - beta-lactamase degrades Nitrocefin which then changes from yellow to red
[E]
[ES]

Question 12

First order rate

Answer 12

v = k[A]

Question 13

Steady State assumption

Answer 13

[ES] constant

Question 14

Michaelis Menten equation

Answer 14

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

Question 15

Km

Answer 15

Dissociation constant of ES

- the lower the Km the higher the affinity of enzyme for substrate

Question 16

Vmax

Answer 16

Maximum catalytic rate at full saturation

- approached asymptotically

Question 17

Linewaver Burke Plot

Answer 17

reciprocal of MM

Question 18

Lineweaver Burke equation

Answer 18

1/v = 1/Vmax + Km/Vmax + [S]

Question 19

y-int on LB plot

Answer 19

1/Vmax

Question 20

x-int on LB plot

Answer 20

-1/Km

Question 21

slope of LB plot

Answer 21

m = Km/Vmax

Question 22

Dihydrofolate reductase

Answer 22

Inhibitor: Methotrexate - used to treat cancer
Substrate: Tetrahydrofolate - role in purine and pyrimidine biosynthesis

Question 23

Competitive Inhibition

Answer 23

• Inhibitor binds to active site
• Increase of [S] overcomes inhibition
• Vmax stays the same
• Km increased

Question 24

Non-competitive Inhibition

Answer 24

• Inhibitor binds to allosteric site
• Inhibitor binds to active site permanently
• Increase of [S] can’t overcome inhibition
• Vmax decreases
• Km stays the same

Question 25

Ki

Answer 25

Dissociation constant for inhibitor

• Vmax = VmaxI (1+([I]/Ki))
• KmI = Km (1+([I]/Ki))

Question 26

Alanine

Answer 26

-ve allosteric modulator for pyruvate kinase

Question 27

Holoenzyme

Answer 27

Apoenzyme + cofactor

Question 28

Vitamin cofactors

Answer 28

A D E K

Question 29

DIPF

Answer 29

Acetylcholinesterase inhibitor reacts with serine residue

Question 30

Vitamin A

Answer 30

Vision, growth, reproduction

Question 31

Vitamin D

Answer 31

Calcium regulation, phosphate metabolism

Question 32

Vitamin E

Answer 32

Antioxidant

Question 33

Vitamin K

Answer 33

Blood coagulation

Question 34

Ascorbate deficiency

Answer 34

Scurvy

Question 35

Cooperativity

Answer 35

Change of substrate binding affinity once the first substrate binds

Question 36

Hexokinase

Answer 36

• highly regulated
• catalyses glucose+ATP
• in brain and skeletal muscle
• high affinity for glucose: low Km
• operated near Vmax at normal blood glucose levels

Question 37

Glucokinase

Answer 37

• catalyses glucose+ATP
• non regulatory
• in liver
• lower affinity for glucose
• at normal blood glucose it operates far below Vmax
• if blood glucose rises it can speed up and take up excess glucose to convert it into glycogen and fat