Date post: | 18-Jan-2016 |
Category: |
Documents |
Upload: | daniella-patrick |
View: | 220 times |
Download: | 0 times |
EnzymeEnzyme Kinetics Kinetics and Mechanismand Mechanism
Karen Cao, Edward Lee, Jennifer Liu, Dea Yong Park, Sharmila
Railkar, Jyotsna Ramachanadran, Jason Stickel, Laura Tiedemann,
Lindsay Vendetta, Kurt Weiberth, Caitlin Williams
•http://biomechanics.ecs.umass.edu/HHPAJX/hhpajx5.gif
What is an enzyme?• Catalyzes a
chemical reaction by lowering activation energy
• Affected by temperature and pH
• Essential within human body
Chasin, Lawrence & Mowshowitz, Deborah. (2006, September). Lec. 6. Biol C2005/F2401 Columbia University. New York, NY. Retrieved on 8 August, 2007 from http://www.columbia.edu/cu/biology/courses/c2005/purves6/figure06-14.jpg
Examples of Enzymes
Enzyme Nonenzymatic t1/2 knon (s-1) kcat
(s-1)Rate enhancement (kcat/knon)
OMP decarboxylase
78 000 000 years 2.8 x 10-16 39 1.4 x 1017
Staphylococcal nuclease
130 000 years 1.7 x 10-13 95 5.6 x 1014
Adenosine deaminase
120 years 1.8 x 10-10 370 2.1 x 1012
AMP nucleosidase
69 000 years 1.0 x 10-11 60 6.0 x 1012
Cytidine deaminase
69 years 3.2 x 10-10 299 1.2 x 1012
CITATION
Enzymes
• Active Site- the specific portion of an enzyme that attaches to the substrate
• Substrate- the reactant on which an enzyme works Campbell, N. A. & Reece
J. B. (2005). Biology. pp. 123
Adenosine Deaminase (ADA)
• T cell development• Neurotransmission• Blood flow• Platelet
aggregation• Regulates
adenosine levels
Adenosine Deaminase 1VFL.png. (2007). Wikipedia. Retrieved August 1, 2007 from http://en.wikipedia.org/wiki/Image:Adenosine_deaminase_1VFL.png
Adenosine
• Critical nucleoside• Backbone of various biological
structuresAdenosine triphosphate (ATP)Cellular receptors (G-proteins)
• Prevents tissue damage during hypoxia, ischemia, and seizure activity
Adenosine to Inosine
ON
OHHO
N
N N
N
CH2OH
NH2 O
CH2OH
N
N N
NH
ON
OHHO
H2O
NH3
Adenosine Inosine
ADA Complications• Severe Combined
Immunodeficiency Syndrome (SCIDS)
• Lymphoma• Hemolytic Anemia
Cavazzana-Calvo, M. & Hacein-Bey, S. Gene Therapy: Bursting the Bubble of SCIDS. (2001). University of Arizone. Retrieved August 1, 2007 from http://student.biology.arizona.edu/honors2000/group08/images/babybubble.jpg
“A T Cell killing a cancer cell.” (2007). T-cells. Retrieved August 3, 2007 from http://www.sciencemuseum.org.uk/on-line/lifecycle/116.asp
How ADA catalyzes
Wilson, D. K. et. al. Atomic Structure of Adenosine Deaminase Complexed with a Transition-State Analog: Understanding Catalysis and Immunodeficiency Mutations. (1991.) Science 252 (5010). 1278.
How ADA catalyzes
Wilson, D. K. et. al. Atomic Structure of Adenosine Deaminase Complexed with a Transition-State Analog: Understanding Catalysis and Immunodeficiency Mutations. (1991.) Science 252 (5010). 1278.
How ADA catalyzes
Wilson, D. K. et. al. Atomic Structure of Adenosine Deaminase Complexed with a Transition-State Analog: Understanding Catalysis and Immunodeficiency Mutations. (1991.) Science 252 (5010). 1278.
How ADA catalyzes
Wilson, D. K. et. al. Atomic Structure of Adenosine Deaminase Complexed with a Transition-State Analog: Understanding Catalysis and Immunodeficiency Mutations. (1991.) Science 252 (5010). 1278.
How ADA catalyzes
Wilson, D. K. et. al. Atomic Structure of Adenosine Deaminase Complexed with a Transition-State Analog: Understanding Catalysis and Immunodeficiency Mutations. (1991.) Science 252 (5010). 1278.
Purpose• Begin attempts to identify
the functional group which protonates the amine leaving group
• pH dependence of two substratesAdenosine6-Chloroadenosine
?
Wilson, D. K. et. al. Atomic Structure of Adenosine Deaminase Complexed with a Transition-State Analog: Understanding Catalysis and Immunodeficiency Mutations. (1991.) Science 252 (5010). 1278.
N
NN
N
NH2
O
OHOH
HH
HH
HO
N
NN
N
Cl
O
OHOH
HH
HH
HO
Adenosine 6-Chloroadenosine
Adenosine 6-Chloroadenosine
Overview of experiment
• Determine rates of reaction of both adenosine and 6-chloroadenosine at varying concentrations and pHs.
• Calculate and compare rate constants to establish which reaction is more sensitive to pH
Why This Works
• At higher pHs, the solution will neutralize the acidic side chain before it can protonate the NH2
• 6-Chloroadenosine does not need a proton to continue with reaction
• Therefore, 6-Chloroadenosine will be less dependent on pH and show higher reaction rates.
The Science Company. (2007). Toward Understanding pH. Retrieved 7 August, 2007 from www.sciencecompany.com/iages/phscale.gif
Projected k2 Graphs
Case 1: pH dependence comes from the protonation of the amine group
Case 2: pH dependence comes from the protonation of the 1N or denaturation of the protein
6-ChloroadenosineAdenosine
Materials• Adenosine solution• Adenosine deaminase• 6-Chloroadenosine• Buffers of varying pH
• Distilled Water• Micropipettes• Microcentrifuge
tubes• Spectrophotometer
Micropipette. (2007). Biokits.com. Retrieved 8 August, 2007 from http://www.biokits.com
DU® 530 Life Science UV/Visible Spectrophotometers. (2007). Retrieved
8 August from http://www.biocompare.com
Procedure
• Use varying concentrations of adenosine solution and 6-chloroadenosine solution at each pH
• Add adenosine deaminase• Run sample through spectrophotometer for
duration of reaction to analyze rate of reaction– Beer’s Law: Abs. concentration
• Compress data and compare reaction rates of adenosine deaminase and 6-chloroadenosine
Absorbance vs. Time of 60 microM 6-Chloroadenosine at pH 8.9 y = -5.12E-05x + 4.38E-01
R2 = 9.92E-01
0.4050.41
0.4150.42
0.4250.43
0.4350.44
0 100 200 300 400 500 600 700
Time (sec.)
Ab
so
rba
nc
e
Absorbance vs. Time of 50 microM Adenosine at pH 8.9
y = -5.75E-04x + 7.01E-01
R2 = 1.00E+00
0.61000.62000.63000.64000.65000.66000.67000.68000.69000.70000.7100
0 20 40 60 80 100 120 140 160
Time (sec.)
Ab
so
rba
nc
e
Michaelis-Menten Kinetics
tEkv ][2max
1
21
k
kkKM
][
][max
sk
svv
mo
Berg, J. M., Tymoczko, J. L., & Stryer, L. (2007.) Biochemistry. (6th ed.) New York: W.H. Freeman and Company.
Michaelis-Menten Chart for 6-Chloroadenosine at pH 8.9
0.00E+00
2.00E-09
4.00E-09
6.00E-09
8.00E-09
1.00E-08
1.20E-08
1.40E-08
1.60E-08
1.80E-08
2.00E-08
0 20 40 60 80 100 120
[S]
Vo
Michaelis-Menten Chart for Adenosine at pH 8.9
0
0.00000001
0.00000002
0.00000003
0.00000004
0.00000005
0.00000006
0.00000007
0.00000008
10
.00
[S]
Vo
Double Reciprocal Plot
maxmax
1
][
11
VSV
K
vM
o
y = m • x + b
Berg, J. M., Tymoczko, J. L., & Stryer, L. (2007.) Biochemistry. (6th ed.) New York: W.H. Freeman and Company.
Double Reciprocal Chart forAdenosine at pH 8.9
y = 4.58E+08x + 3.11E+06R2 = 9.88E-01
0
10000000
20000000
30000000
40000000
50000000
60000000
0 0.02 0.04 0.06 0.08 0.1 0.12
1/[S]
1/V
o
Double Reciprocal Chart for6-Chloroadenosine at pH 8.9
y = 3.64E+09x + 3.11E+07
R2 = 9.84E-01
0
100000000
200000000
300000000
400000000
500000000
600000000
700000000
800000000
0.00 0.05 0.10 0.15 0.20 0.25
1/[S]
1/V
o
pH k2(Ad) pH k2(Cl-Ad)
7.3 68.3 7.3 0.26
8.4 30.6 8.4 0.319
8.9 4.62 8.9 0.77
9.4 1.63 9.4 <0.08
pH vs. k2 for Adenosine and
6-Cl-Adenosine
0
20
40
60
80
7 7.5 8 8.5 9 9.5 10pH
Adenosi
ne k
2
0
0.2
0.4
0.6
0.8
6-C
l-A
denosi
ne k
2
Adenosine 6-chloroadenosine
Conclusions
2 preliminary conclusionsAdenosine is more pH sensitive than 6-
chloroadenosineImportance of acidic side chains and
protonation of amine group in pH dependence
Further Testing
• Determinations of more k₂ valuesTest adenosine and 6-Cl-adenosine at
more pH’s and more concentrations
• Testing of individual amino acid groups within enzymeReplacement of amino acid groups via
mutagenesis
Applications
• Comprehension of underlying ADA catalysis mechanism allows for more effective ADA inhibitors
• Major medical implicationsSCIDSLymphomasMetabolic disorders
Thank You
• Prudential and other sponsors• Dr. Miyamoto• Dr. Steven Surace• Dr. Paul Victor Quinn, Sr.• Myrna Papier• Dr. Adam Cassano• Jen Cowell
Sources1. Campbell, N. A. & Reece J. B. (2005). Biology. 1232. Adenosine Deaminase 1VFL.png. (2007). Wikipedia. Retrieved
August 1, 2007 from http://en.wikipedia.org/wiki/Image:Adenosine_deaminase_1VFL.png
3. “A T Cell killing a cancer cell.” (2007). T-cells. Retrieved August 3, 2007 from http://www.sciencemuseum.org.uk/on-line/lifecycle/116.asp
4. Cavazzana-Calvo, M. & Hacein-Bey, S. Gene Therapy: Bursting the Bubble of SCIDS. (2001). University of Arizone. Retrieved August 1, 2007 from http://student.biology.arizona.edu/honors2000/group08/images/babybubble.jpg
5. Wilson, D. K. et. al. Atomic Structure of Adenosine Deaminase Complexed with a Transition-State Analog: Understanding Catalysis and Immunodeficiency Mutations. (1991.) Science 252 (5010). 1278.
6. Berg, J. M., Tymoczko, J. L., & Stryer, L. (2007.) Biochemistry. (6th ed.) New York: W.H. Freeman and Company.
Sources• Catalysis. http://www.columbia.edu/cu/biology/courses/c2005/purves6/figure06-14.jpg
• http://upload.wikimedia.org/wikipedia/commons/thumb/c/c6/Adenosine_deaminase_1VFL.png/593px-Adenosine_deaminase_1VFL.png
• Slide 1 http://biomechanics.ecs.umass.edu/HHPAJX/hhpajx5.gif