enzyme mechanisms

Question 1

_____ inhibitors modify or destory a catalytic functional group

Answer 1

irreversible

Question 2

enzyme activity is ___ dependent; each amino acid has an optimum

Answer 2

pH

Question 3

pH optimum may give clues to identify catalytic ____

Answer 3

residues

Question 4

example question: an amino acid residue that may directly participate in reaction catalyzed by pepsin is (pH 2; need amino acid that ionizes at this pH)

Answer 4

glutamic acid

Question 5

___ proteases catalyze the hydrolytic cleavage of peptide bonds

Answer 5

serine

Question 6

why would we need to cleave peptide bonds

Answer 6

break up proteins
pro peptides

Question 7

3 need to know serine proteases

Answer 7

trypsin, chymotrypsin, elasatse

Question 8

chymotrypsin is made up of three different chains; which shows it has what level of organization

Answer 8

quartenary

Question 9

chymotrypsin has ___ disulfide bonds and cleaves large peptide bonds at aromatic amino acids

Answer 9

5

Question 10

chymotrypsin has catalytic triad which is

Answer 10

histidine 57, aspartate 102, and serine 195

Question 11

chymotrypsin catalyzes peptide hydrolysis but it does not use direct addition of ____ to peptide bond

Answer 11

water

Question 12

what is the two step mechanism which chymotrypsin uses

Answer 12

acylation (fast) and deacylation (slow)

Question 13

the active site residues on chymotripsin contains what

Answer 13

catalytic triad

Question 14

the substrate binding pocket of chymotrypsin binds what

Answer 14

aromatics

Question 15

what does chymotrypsin act on to make p-nitrophenolate (cleaves ester not just peptide)

Answer 15

p-nitrophenylacetate

Question 17

chymotrypsin in p-nitrphenol uses what mechanism

Answer 17

fast step: enzyme acetylation and release of p-NP
slow step: hydrolysis of acyl-enzyme intermediate to deacylate it (Allows it to be active has serine OH group)

Question 18

the catalytic triad is ___ bonded from Ser195-His57-Asp102

Answer 18

H

Question 19

the specificity of the serine proteases arises from specificity pocket what is chymotrypsin’s

Answer 19

hydrophobic pocket (stabilizes aromatic ring)

Question 20

in the chymotrypsin reaction mechanism water does not directly attack the peptide bond but the ____ bond

Answer 20

acyl

Question 21

the chymotrypsin mechanism is a good example of what three components

Answer 21

• general acid base catalysis
• transition state stabilization
• covalent catalysis

Question 22

in the chymotrypsin mechanism His 57 acts as a __ ___ which abstracts proton from _____

Answer 22

general base; ser195

Question 23

His57+ is stabilizes by ____ carboxylate

Answer 23

Asp102

Question 24

Ser195 O- (Active site) is reasy to attack as a nucleophile the C double O of ____ bond

Answer 24

peptide

Question 25

____ bonded chain makes Ser a better nucleophile

Answer 25

H