Enzymes 3

Question 1

What is the common proteolysis example

Answer 1

Serine proteases are enzymes that cleave peptide bonds in proteins. Serine serves as the nucleophilic amino acid at the (enzyme’s) active site.

Question 2

What can bind to Elastase active site?

Answer 2

small side chains

Question 3

What can bind to Chymotrypsin active site?

Answer 3

SP (lined by hydrophobic residues)

Question 4

What can bind to Trypsin active site?

Answer 4

+ charged side chains

Question 5

State the 5 point overview of the nucleophilic attack between His and Ser

Answer 5

1. Formation of nucleophile by catalytic triad
2. His removes H+ from Ser (acid base catalysis)
3. Ser becomes strong nucleophile which reacts with substrate ( covalent catalysis)
4. DIPF reacts with Ser
5. TPCK reacts with His

Question 6

Describe the diagram to show step 1

The nucleophilic attack on polypeptide carbonyl

Answer 6

His bind to Ser.
Arrow from Histine’s N to bond between N and H
Arrow from bond between same H and O to C from other molecule.

N-H-O then NH-CO

Question 7

Describe the diagram to show step 2

Covalent intermediate

Answer 7

Positively charged Histine
Arrow from NH bond to N in His
Arrow from NH-C0- bond to H of NH

Question 8

Describe the diagram to show step 3

Cleavage and loss of C-terminal fragment

Answer 8

N-H-NH etc on His

COOR

Question 9

Describe the diagram to show step 4

Nucleophilic attack on polypeptide carbonyl by H20

Answer 9

Arrow from N in His to H in H20

Arrow from OH bond in water to C in COOR

Question 10

Describe the diagram to show step 5

Covalent intermediate of Oxyanion hole

Answer 10

Positively charged His

Arrow from CO bond to N in His

Question 11

Describe the diagram to show step 6

Cleavage and loss of N-terminal fragment

Answer 11

N—–H-O- rest of moelcule