lecture 3: proteases

0.0(0)
Studied by 0 people
call kaiCall Kai
learnLearn
examPractice Test
spaced repetitionSpaced Repetition
heart puzzleMatch
flashcardsFlashcards
GameKnowt Play
Card Sorting

1/10

encourage image

There's no tags or description

Looks like no tags are added yet.

Last updated 2:26 PM on 6/5/26
Name
Mastery
Learn
Test
Matching
Spaced
Call with Kai
Chat

No analytics yet

Send a link to your students to track their progress

11 Terms

1
New cards

scissile bond

where the hydrolysis occurs

2
New cards

chymotrypsin

serine protease

3
New cards

the main amino acids in chymotrypsin

  • asp102

  • his57

  • ser195


4
New cards

specific modification of the essential ser195 to identify the structure of chymotrypsin

  • PMSF: the -OH on the ser attacks the PMSF, forming a covalent bond and inhibiting the enzyme

  • DIPF: blocks the enzyme and related molecules (like acetylcholine esterase)


5
New cards

chemical labelling of the essential active site His57

  • TPCK: His57 does a nucleophilic attack on the chloromethyl ketone group of the TPCK. the Cl- is kicked out and a covalent bond forms between the His and TPCK

  • this causes the enzyme to be inactive/ reduced by 1000-fold


6
New cards

the catalytic triad

  • interactions of the ser195, his57 and asp102 makes it easier to stabilise the negative charge on the ser

  • the negative charge on asp102 stabilises the formation of the positive form of his57, by enabling a charge relay that allows his57 to abstract ser195’s H+


7
New cards

chymotrypsin mechanism

  • Acylation:

    1. The substrate binds in the specificity pocket, orienting the scissile bond.

    2. His57 pulls a H+ from Ser195

    3. The activated Ser195 oxygen attacks the carbonyl carbon of the substrate, forming a tetrahedral intermediate stabilized by the oxyanion hole.

    4. The intermediate collapses; the peptide bond breaks, and the C-terminal half of the protein leaves the active site. The N-terminal half remains covalently bonded to the enzyme as an acyl-enzyme intermediate.

  • Deacylation :

    1. A water molecule enters the active site.

    2. His57 pulls a H+ from the water to create a hydroxide ion.

    3. This hydroxide attacks the acyl-enzyme intermediate, forming a second tetrahedral intermediate.

    4. The intermediate collapses, releasing the remaining part of the substrate and restoring the catalytic triad to its original state.


<ul><li><p><strong>Acylation:</strong></p><ol><li><p>The substrate binds in the specificity pocket, orienting the scissile bond.</p></li><li><p>His57 pulls a H+ from Ser195 </p></li><li><p>The activated Ser195 oxygen attacks the carbonyl carbon of the substrate, forming a tetrahedral intermediate stabilized by the oxyanion hole.</p></li><li><p>The intermediate collapses; the peptide bond breaks, and the C-terminal half of the protein leaves the active site. The N-terminal half remains covalently bonded to the enzyme as an acyl-enzyme intermediate.</p></li></ol></li><li><p><strong>Deacylation :</strong></p><ol><li><p>A water molecule enters the active site.</p></li><li><p>His57 pulls a H+ from the water to create a hydroxide ion.</p></li><li><p>This hydroxide attacks the acyl-enzyme intermediate, forming a second tetrahedral intermediate.</p></li><li><p>The intermediate collapses, releasing the remaining part of the substrate and restoring the catalytic triad to its original state.</p></li></ol></li></ul><p></p>
8
New cards

where is the oxyanion hole located

near the carbonyl group of the scissile bond

9
New cards

what is the oxyanion hole

a region in the active site where the backbone amide hydrogens of ser195 and gly193 point into the active site cavity

10
New cards

why are the amino acids positioned in a certain way in the oxyanion hole

so that thenegatively-charged tetrahedral enzyme-substrate intermediate is stabilised

11
New cards

how much does the oxyanion hole increase enzyme activity

by 10000x