L2 Mechanisms of enzymes

Question 1

What are the benefits of the conformational change in hexokinase when transforming Glucose to Glucose-6-phosphate?

Answer 1

(1) Positions ATP to facilitate phosphoryl group transfer
(2) Exclusion of water from the active site, to eliminate energy barrier caused by ordered water molecules surrounding glucose and avoid ATP hydrolysis

Question 2

How many catalytic amino residues do enzymes usually have in their active sites?

Answer 2

2-6

Question 3

What catalysis creates a strong nucleophilic reactant for further reaction, base catalysis or acid catalysis?

Answer 3

base catalysis

Question 4

Covalent catalysis is also known for what catalysis?

Answer 4

Nucleophilic catalysis

Question 5

What does scissile bond mean?

Answer 5

Peptide bond to be cleaved

Question 6

What are the effects of the enzyme on chemical reactions?

Answer 6

(1) They lower the activation energy of reactions
(2) They stabilize transition states during catalysis
(3) They make substrates more reactive by forming enzyme-substrate complex

Question 7

What is the definition of acid-base catalysis?

Answer 7

A proton is transferred between the enzyme and the substrate

Question 8

What can act as acid-base catalysts?

Answer 8

Amino acid side chains:
(1) Asp
(2) Glu
(3) His
(4) Lys
(5) Cys
(6) Tyr

Question 9

In base catalysis, the catalytic AA residue receive a proton or donate a proton?

Answer 9

Receive a proton

Question 10

In acid catalysis, when will the covalent bond is cleaved more easily?

Answer 10

When one of catalytic AA’s atom is protonated

Question 11

What can act as covalent catalysts?

Answer 11

Amino acid side chains:
(1) Ser, Tyr
(2) Cys
(3) Lys
(4) His