Lecture 17

Question 1

The induced fit model (Daniel Koshland)

Answer 1

The shape of the active site does not fully match the substrate until binding has taken place

• initial weak binding of the substrate induces changes in enzyme structure
• strong binding effect on the structure of the transition state

Question 2

three factors of enzyme catalysis

Answer 2

1) Enzyme brings reacting groups together at the active site in the orientation required for reaction
2) Some amino acid side chains act as acid or base catalysts, many enzymes also rely on metal ion catalysts at the active site
3) Amino acid side chains can stabilize transition states and intermediates by dispersion forces, electrostatic interactions and hydrogen bonding

Question 3

Oxidoreductases

Answer 3

Catalyze redox reactions

Question 4

transferases

Answer 4

Catalyze the movement of functional groups (including alkyl groups)

Question 5

Hydrolases

Answer 5

Catalyze hydrolysis reactions

Question 6

Lyases

Answer 6

Cleave covalent bonds by other means than redox or hydrolysis reactions

Question 7

Isomerases

Answer 7

Catalyze molecular isomerizations

Question 8

Ligases

Answer 8

Join two molecules together with covalent bonds

Question 9

General acid catalysis

Answer 9

• common for enzyme reactions
• Protonation happens during the rate limiting step
• Proton transfer and nucleophilic attack occur at the same time

Question 10

General base catalysis

Answer 10

occurs when the substrate is deprotonated by a catalytic side chain or when the proton is relayed through a water molecule