Enzyme mechanisms

Question 1

List the 6 ways in which the binding of substrates to enzymes speeds up reactions

Answer 1

1. Weakening bonds in substrates
2. Stabilising the transition state
3. Increasing the local concentration of substrates
4. Holding the substrates in the correct orientation
5. Altering the microenvironment
6. Converting complex reactions into a series of bimolecular reactions

Question 2

What are the 4 catalytic principles?

Answer 2

1. Covalent catalysis
2. General acid-base catalysis
3. Metal ion catalysis
   - Electrophilic catalysis
   - Generation of nucleophile
   - Co-substrate (increase binding interactions)
4. Catalysis by enhanced proximity)

Question 3

What does chymotrypsin do?

list the 4 amino acids too

Answer 3

Cleaves peptide bonds selectively on the C-terminus of large or aromatic hydrophobic (non polar) amino acids such as tryptophan, tyrosine, phenylalanine, and methionine

Question 4

What type of catalysis is chymotrypsin a good example of?

Answer 4

Covalent catalysis

Question 5

Describe why proteases facilitate a fundamentally difficult reaction (clue: features of the peptide bond) and therefore what must the enzyme do?

Answer 5

The chemical nature of peptide bonds is that the resonance structure that accounts for their planarity makes them resistant to hydrolysis.

They have a partial double bond character (the C-N bond). The carbonyl carbon atom is less electrophilic and less susceptible to nucleophilic attack so an enzyme must promote peptide bond cleavage by by facilitating a nucleophilic attack at a normally unreactive carbonyl group