ChemoWorksheet14 - BIOC*2580
Lecture
14:


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Unformatted text preview: BIOC*2580
Lecture
14:
 The
Catalytic
Mechanism
of
Chymotrypsin
‐‐
Worksheet
 1
 
 
 
 
 Step
1:
Nucleophilic
Attack
 a) His‐57
acts
as
a

_______
 _________,
removing
H+
 from
Ser‐195
 
 b) Ser‐195
becomes
a
better
 ______________,
attacks
 peptide
C=O
 
 c) Negative
charge
on
Asp‐ 102
________
positive
on
 His‐57.
 
 
 
 Formation
of
the
First
 Transition
State
(T.S.)
 a) ________________
pulls
 the
O‐
into
the
T.S.
 
 
 • ____________
to
the
T.S.
 
 
 • favours
______________
 __________
configuration
 
 
 
 
 Breakdown
of
First
T.S.
 Formation
of
Acyl‐Enzyme
 Intermediate
 a) NH
group
of
substrate
 acts
as
______________
 
 b) His‐57
acts
as
a
________
 __________,
donating
H+
 to
the
leaving
group
 
 c) C‐terminal
peptide
leaves
 
 d) N‐terminal
peptide
 remains
covalently
 bound:
the
acyl‐enzyme
 intermediate
 BIOC*2580
Lecture
14:
 The
Catalytic
Mechanism
of
Chymotrypsin
‐‐
Worksheet
 2
 
 
 
 
 Step
2:

Nucleophilic
Attack
 a) water
now
enters
the
 catalytic
site
 
 b) His‐57
acts
as
a
________
 _________,
removing
H+
 from
water
 
 c) Water
becomes
a
better
 ___________,
attacks
the
 acyl‐enzyme
C=O
 
 
 
 
 Formation
of
the
Second
 Transition
State
(T.S.)
 a) ________________
 stabilizes
the
T.S.
 configuration
 
 
 
 
 
 
 
 
 
 Breakdown
of
Second
T.S.
 Formation
of
Products
 a) His‐57
acts
a
__________
 _____,
donating
H+
to
Ser‐ 195
 
 b) Breaks
the
_______
bond
 
 c) N‐terminal
peptide
leaves
 
 d) Catalytic
triad
is
 ___________________
 
 
 
 
 
 ...
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This note was uploaded on 09/21/2011 for the course BIOOC 2580 taught by Professor Douger during the Fall '10 term at University of Guelph.

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