Exam 2: Chp 14

Question 1

What are 3 catalytic strategies of enzymes?

Answer 1

1) Covalent
2) Acid-Base
3) Metal ion

Question 2

How is covalent catalysis performed?

Answer 2

Enzyme forms covalent bond to substrate during reaction

Question 3

What properties are required for covalent catalysis?

Answer 3

An AA in the active site must be a good nucleophile and good LG later to regenerate the enzyme

Question 4

What is specific acid/base catalysis?

Answer 4

H+ or OH- diffuses in solution

Question 5

What is general acid/base catalysis?

Answer 5

H+ or OH- created in transition state via another molecule or group

Question 6

What is a metalloenzyme?

Answer 6

An enzyme closely associated with a metal ion

Question 7

How do metal ions facilitate catalysis?

Answer 7

Positively charged electrophiles that stabilize e- density or formal negative charges

Question 8

What are two examples of a serine protease?

Answer 8

Trypsin and chymotrypsin

Question 9

What is the function of a protease?

Answer 9

to cleave a peptide bond

Question 10

What is the function of an esterase?

Answer 10

to cleave an ester bond

Question 11

What is highly conserved between serine proteases and esterases?

Answer 11

A catalytic triad of Ser, His, and Asp

Question 12

What can be replaced with what in the catalytic triad of serine proteases and estrerases?

Answer 12

Asp with Glu

Question 13

Why is His included in the catalytic triad of serine proteases and estrerases?

Answer 13

Have a good pKa for acid base rxns

Question 14

Why is Ser included in the catalytic triad of serine proteases and estrerases

Answer 14

is a 1° alcohol and functions as nucleophile in reaction

Question 15

What is the fast step of a chymotrypsin cleavage?

Answer 15

The serine performs nucleophilic attack on substrate’s carbonyl carbon

Question 16

What is the slow step of a chymotrypsin cleavage?

Answer 16

hydrolysis to release the rest of substrate

Question 17

How does aspartic protease cleave peptide bonds?

Answer 17

Using 2 aspartic acid residues to cleave between 2 hydrophobic AAs

Question 18

What is the structure of an aspartic protease?

Answer 18

2 domains that are similar to form a symmetrical protein

Question 19

Do serine proteases and esterases form a covalent intermediate?

Answer 19

Yes

Question 20

Do aspartic acid proteases form a covalent intermediate?

Answer 20

No

Question 21

What kind of catalysis do aspartic proteases employ?

Answer 21

general acid/base catalysis

Question 22

What kind of protease is HIV protease?

Answer 22

An aspartic protease

Question 23

Why chorismate mutase unique in the reaction it catalyzes?

Answer 23

The reaction will still occur, just very slow

Question 24

Why does chromate mutase catalyze formation of prephenate from chorismate?

Answer 24

stabilizes near attack conformation