investigation on enzyme activity and kinetics

7/17/2019 INVESTIGATION ON ENZYME ACTIVITY AND KINETICS

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UNIVERSITI TEKNOLOGI MARA

FAKULTI KEJURUTERAAN KIMIABIOPROCESS ENGINEERING LABORATORY

(CBE 661)

No. Title Allocated Marks Marks1. Abstract/Summary 52. Introduction 5

3. Aims 54. Theory 55. Apparatus 56 Methodology/Procedure 107. Results 108. Calculations 109. Discussion 2010. Conclusion 1011. Recommendations 512. Reference 513. Appendices 5

TOTAL 100

Remarks:

Checked by: Rechecked by:

……………………………......... ……………………………..

Date: Date:

NAME AND MATRIC NO : MUHAMMAD ARSHAD BIN ABDUL RASHID

(2014683386)

GROUP : 5

EXPERIMENT : LAB 5 (INVESTIGATION ON ENZYME ACTIVITY

AND KINETICS)

DATE PERFORMED : 29 SEPTEMBER 2015

SEMESTER : 5

PROGRAMME CODE : EH242 5E

SUBMIT TO : PN SUHAILA BT MOHD SAUID



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Table of Contents

NO. TITLE PAGES

1 Abstract 3

2 Introduction 4

3 Objectives 5

4 Theory 5

5 Apparatus 9

6 Methodology/Procedure 9

7 Results 11

8 Calculations 18

9 Discussion 20

10 Conclusion 22

11 Recommendations 23

12 Reference 23

13 Appendices 24



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Abstract

Enzymes are protein catalysts that speed up chemical reaction in living organisms. Thisinvestigation tested the effects of temperature and pH has on enzyme activity. The 2% starchsolution was treated with different temperature (30 ͦ C, 40 ͦ C, 50 ͦ C and 60 ͦ C), pH (5,6, 7, 8 and9) and the substrate concentration (0.5%, 1.5%, 2.0%, 2.5% and 3.0%). Data was collected by

determine the enzyme activity and the absorbance value at λ=540 nm. The objective for thisexperiment is determination of the effects of temperature on the enzymatic activity and changesin enzyme concentration of an enzyme-catalyzed reaction. It is also describe the relationshipbetween substrate concentration and the maximum velocity of an enzyme. After conducting theexperiments we can see that different temperature, pH and substrate concentration give differentenzyme activity and the absorbance value. From the pH experiment we can see the optimum pHfor amylase is at pH 6, the optimum temperature we fail to determine due to some error whileconducting the experiment while the higher substrate concentration the lower the enzyme activity.This experiment has shown that enzymes must have certain environmental conditions present inorder for them to function properly. With this knowledge, one can successfully performexperiments using enzymes in the future by making sure that the environmental conditionspresent are optimum for the enzyme that is being used.



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Introduction

Cells function largely because of the action of enzymes. Life is a dynamic process that involves

constant changes in chemical composition. These changes are regulated by catalytic reactions,

which are regulated by enzymes. At one time, the cell was actually conceived of as a sac of

enzymes. It was believed that if we knew all of the reactions and their rates of action, we could

define the cell, and indeed, life itself. Few biologists continue to think of this as a simple task, but

we know that life as we know it could not exist without the function of enzymes. Ideally, we would

examine enzymes within an intact cell, but this is difficult to control. Consequently, enzymes are

studied in vitro after extraction from cells.

Enzymes are protein molecule that acts as biological catalysts. Without changing of the

overall process, they increase the rate of reactions. Enzymes are long chains of amino acids

bound together by peptide bonds. Besides that, they are seen in all living cells and controlling the

metabolic processes in which they converted nutrients into energy and new cells. Other than that,

enzymes also help in the breakdown of food materials into its simplest form. The reactants of

enzyme catalyzed reactions are termed substrates and each enzyme is quite specific in character,

acting on a particular substrates to produce a particular products. The central approach for

studying the mechanism of an enzyme-catalyzed reaction is to determine the rate of the reaction

and its changes in response with the changes in parameters such as substrate concentration,

enzyme concentration, pH, temperature and known as enzyme kinetics. The substrate

concentration, is one of the important parameter that affecting the rate of a reaction that catalyzed

by an enzyme. However, studying the effects of substrate concentration is elaborated by the fact

that during the course of an in vitro reaction, substrate changes due to the conversion of substrate

to product. In this experiment we can see how substrate concentration, pH and temperature effect

the enzyme activity.

Amylase is a type of enzyme. Amylase has an active site organized in subsites, each of

which accommodates a glucose residue (Talamond, Noirot & de Kochko, 2005). It breaks down

starch to glucose, giving food that sweet taste. An example of amylase in the natural world is in

bananas. When they are green, the amylase has yet to break down the starch, but by the time

they’ve turned brown, the reaction has been completed. This is why brown bananas taste sweeter

than their green counterpart.



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Objectives

Determination of the effects of temperature on the enzymatic activity and changes in

enzyme concentration of an enzyme-catalysed reaction.

Describe the relationship between substrate concentration and the maximum velocity of

an enzyme.

Estimation of Michaelis-Menten parameters, effect of pH and temperature on enzyme

activity and kinetics of inhibition.

Theories

Enzymes are protein molecules that act as biological catalysts by increasing the rate of reactions

without changing the overall process. They are long chain amino acids bound together by peptide

bonds. Enzymes are seen in all living cells and controlling the metabolic processes in which they

converted nutrients into energy and new cells. Enzymes also help in the breakdown of food

materials into its simplest form. The reactants of enzyme catalyzed reactions are termed as

substrates. Each enzyme is quite specific in character, acting on a particular substrates to

produce a particular products. The central approach for studying the mechanism of an enzyme-

catalyzed reaction is to determine the rate of the reaction and its changes in response with the

changes in parameters such as substrate concentration, enzyme concentration, pH, temperature

etc .This is known as enzyme kinetics.

One of the important parameters affecting the rate of a reaction catalyzed by an enzyme is the

substrate concentration. During enzyme substrate reaction, the initial velocity V0 gradually

increases with increasing concentration of the substrate. Finally a point is reached, beyond which

the increase in V0 will not depend on the substrate concentration. When we plot a graph with

substrate concentration on the X axis and corresponding velocity on Y axis. It can be observed

from the graph that as the concentration of the substrate increases, there is a corresponding

increase in the V0. However beyond a particular substrate concentration, the velocity remains

constant without any further increase. This maximum velocity of an enzyme catalyzed reaction

under substrate saturation is called the Vmax , Maximum velocity.



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Figure 4.1: Graph of initial velocity against substrate concentration (Nelson, D.L et. al, n.d)

Michaelis – Menten Equation

Leonor Michaelis and Maud Menten postulated that the enzyme first combines reversibly with its

substrate to form an enzyme-substrate complex in a relatively fast reversible step:

Eqn.1

In the next step, this ES complex is breaks down in to the free enzyme and the reaction product,P:

Eqn.2

Since the second step is the rate limiting step, the rate of overall reaction must be proportional to

the concentration of the ES that reacts in the second step. The relationship between substrate

concentration, substrate and Initial velocity of enzyme, V0 has the same general shape for most

enzymes (it approaches a rectangular hyperbola). This can be expressed algebraically by theMichaelis-Menten equation. Based on their basic hypothesis that the rate limiting step in

enzymatic reactions is the breakdown of the ES complex to free enzyme and product, Michaelis

and Menten derived an equation which is;



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Eqn.3

The necessary terms in this reaction are S, V0, Vmax, and Km (Michaelis constant). All these

terms can be measured experimentally.

Lineweaver – Burke Plot

In 1934, Lineweaver and Burke made a simple mathematical alteration in the process by plotting

a double inverse of substrate concentration and reaction rate.

Eqn.4

For enzymes obeying the Michaelis-Menten relationship, the “double reciprocal” of the V0 versus

S from the first graph, yields a straight line. The slope of this straight line is KM /Vmax, which has

an intercept of 1/Vmax on the 1/V0 axis, and an intercept of -1/KM on the 1/[S] axis. The double-

reciprocal presentation, also called a Lineweaver-Burk plot. The main advantage of Lineweaver-

Burk plot is to determine the Vmax more accurately, which can only be approximated from a

simple graph of V0 versus S.

Figure 4.2: Lineweaver-Burk plot. (Nelson, D.L et. al, n.d)



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The enzyme α Amylase can catalyze the hydrolysis of internal α -1,4-glycosidic bond present in

starch with the production of reducing sugars. In the study of substrate concentration on enzyme

kinetics, the enzyme is kept constant where as the concentration of Starch is taken in increasing

order. As the substrate concentration increases, the amount of products produced in everysuccessive tube also increases. This was explained by Michealis and others that an enzyme

catalyzed reaction at varying substrate concentrations is diphasic i.e. at low substrate

concentration the active sites on molecules (enzyme) are not occupied by substrate and the

enzyme rate varies with substrate molecules concentration (phase1). As the number of substrate

molecules increases, the enzyme attains the saturation level, since there is no more reaction sites

remaining for binding. So the enzyme can work with full capacity and its reaction rate is

independent of substrate concentration. (Phase II).

This Enzyme – substrate reaction can be determined by measuring the increase in reducing

sugars using the 3, 5 Dinitro salycilic acid reagent. In an alkaline condition, the pale yellow colored

the 3, 5- dinitro salicylic acid undergo reduction to yield orange colored 3- amino -5-nitrosalicylic

acid. The absorbance of resultant solutions is read at 540nm. The intensity of color depends on

the concentration of reducing sugars produced.

α Amylase

Starch Maltose + glucose

Figure 4.3: The enzyme-substrate reaction example. (vlab.amrita.edu, 2011)



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Apparatus

1. Alpha Amylase enzyme

2. Starch

3. pH buffer solution (pH 4-9)

4. DNSA Reagent

5. Beaker

6. Measuring cylinder

7. Cuvette

8. Falcon tube rack

9. Falcon tube

10. Micropipet and tips11. Label sticker

12. Schott bottle

13. Vortex mixer

14. Water bath

15. Spectrophotometer

16. Hotplate

Procedure

i. Preparation of 2% Starch Solution

a) 4 g of soluble starch is mixed in approximately 50 ml of cold water.

b) While stirring, the slurry is added to approximate 100 ml of gently boiling water in a large beaker.

c) Then the final volume of 200ml is topped up and mix well.

ii. Effect of pH on the activity and stability of amylase enzyme.

a) Five test tubes is labelled with pH 5, 6, 7, 8 and 9. In each tube, 1 mL of 2% starch solution is

placed and 1 mL of the appropriate buffer is added (at corresponding pH) to each tube.

b) Five additional clean test tubes is added and 2 mL of amylase solution was put in each tube.



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c) All 10 tubes is placed in the 37°C water bath for about 5 minutes to allow the temperature to

equilibrate.

d) The content of each amylase test tube is poured into each starch test tube and mixed on vortex

mixer.

e) The tubes is returned to the 37°C water bath.

f) The hydrolysis reaction is proceed for exactly 10 minutes.

g) The amylase activity is determined using the method given in Appendix 1.

h) Graph of pH vs. enzyme activity is plotted.

iii. Effect of temperature on the activity and stability of amylase enzyme.

a) One test tube is labelled with 30ºC. In the tube, 1 mL of 2% starch solution and 1 mL of pH=7

buffer is placed to the tubes.

b) Additional clean test tub is added and 2 mL of amylase solution is put in the tube.

c) Both tubes is placed in the 30°C water bath for about 5 minutes to allow the temperature to

equilibrate.

d) The contents of the amylase is poured test tube into starch test tube and mix them on vortex

mixer.

e) Return the tubes to the 30°C water bath.

f) Let the hydrolysis reaction proceeded for exactly 10 minutes.

g) The amylase activity is determined using the method given in Appendix 1.

h) Step a-g is repeated at 4 different temperatures ranging from 30-70 ºC.

i) Graph of temperature vs. amylase activity is plotted.

iv. Effect of substrate concentration on the activity of amylase enzyme.

a) Starch solutions of varying concentration (0.5, 1.5, 2.0, 2.5, and 3.0% w/v) is prepared as the

substrate.

b) Each tube is labelled with starch concentration and place 1ml of each starch solution into the

test tubes.

c) 1 mL of pH=7 buffer is added to the tubes.

d) Five additional clean test tubes is added and put 2 mL of amylase solution in each tube.

e) All tubes is placed in the 37°C water bath for about 5 minutes to allow the temperature to

equilibrate.



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f) The content of each amylase is poured test tube into starch test tube and mix them on vortex

mixer.

g) Return the tubes to the 37°C water bath.

h) Let the hydrolysis reaction proceed for exactly 10 minutes.

i) The amylase activity is determined using the method given in Appendix 1.

j) Graph of starch concentration against amylase activity is plotted.

Appendix 1 (Demonstration of Enzyme Activity)

a. After 10 minutes (the time of hydrolysis reaction), the reaction is stopped by adding 4 ml of

DNS reagent.

b. Then it is boiled for 10 minutes and then left to cool to room temperature.

c. The absorbance of the samples is measured at λ=540 nm.

d. The absorbance value is compared with glucose standard curve prepared to obtain the glucose

concentration.

e. The enzyme activity is calculated.

Note: Enzyme activity is the amount of glucose formed in reaction mixture per unit time.

Appendix 2 (Glucose Standard Curve Preparation)

a. The standard solutions of glucose is prepared at five different concentrations ranging from 0-

1000mg/L by serial dilution.

b. 1 ml of each glucose solution is added in test tubes.

c. 1 ml of DNS reagent is added in each tube and mix for few seconds on vortex mixer.

d. The test tubes is placed in water bath (T=100°C) for 10 min and then left to cool at room

Results

The obtained results that being recorded from the experiment of investigation on enzyme activity

and kinetics.

Glucose Standard Curve

Table 7.1: The values of absorbance optical density (OD) at five different concentration of glucose



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No.

Glucose

Concentration (g/L)

Absorbance Optical

Density (OD) (nm)

1 200 0.378

2 400 0.668

3 600 0.801

4 800 1.224

5 1000 2.052

The data on the table 7.1 above is used to plot the standard curve of absorbance optical density

(OD) (nm) against glucose concentration (g/L). These obtained results were recorded based on

the observation through the spectrophotometer which already set up at 540 nm.

Figure 7.1: The standard curve of absorbance optical density (OD) (nm) against glucose

concentration (g/L)

The effect of pH to enzyme activity

Table 7.2: The values of absorbance optical density (OD) at five different pH Values.

No. pH Value Absorbance Optical Density (OD) (nm)

1. 5 2.680

y = 0.0018x

R² = 0.89

0

0.5

1

1.5

2

2.5

200 400 600 800 1000

A b s o r b a n c e O

p t i c a l D e n s i t y ( O D )

Concentration (g/L)

A graph of Absorbance Optical Density (OD) against

Concentration



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2. 6 5.170

3. 7 2.625

4. 8 2.546

5. 9 2.350

The table 7.2 above showed the reading of absorbance optical density (OD) (nm) which affected

by five different pH Value.

Figure 7.2: The effect of absorbance Optical Density (OD) (nm) reading at different pH Values

The plotted graph as shown in figure 7.2 showed the five different pH Values which affect the

absorbance Optical Density (OD) (nm) reading. The absorbance Optical Density (OD) (nm)

reading was rapidly increasing from the pH 5 until pH 6 which known as the optimum pH for the

amylase enzyme and the absorbance Optical Density (OD) values is 5.170 nm.

Table 7.3: The values of enzyme activity at different pH

pH

value

Absorbance

reading (nm)

Glucose

concentration,

X (g/mL)

Glucose

released (mol)

Enzyme

activity, V

(mol/min)

5 2.680 0.0015 8.26×10-6 8.26×10-7

0

1

2

3

4

5

6

5 6 7 8 9

A b s o r b a n c e O p t i c a l D e n s i t y ( O D

) ( n m )

pH Value

A graph of absorbance Optical Density (OD) (nm) against pH

Value



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6 5.170 0.0029 1.59×10-5 1.59×10-6

7 2.625 0.0015 8.09×10-6 8.09×10-7

8 2.546 0.0014 7.80×10-6 7.80×10-7

9 2.350 0.0013 7.26×10-6 7.26×10-7

The table 7.3 above showed the calculated values that obtained according to the effect of five

different pH values against the reading of the absorbance optical density (OD) (nm).

Figure 7.3: The effect of enzyme activity against pH values

Based on the observation, the graph that plotted in the figure 7.3 showed the higher values of

enzyme activity was occurred at pH 6 or optimum pH. The enzyme is more reproducible during

the optimum pH.

The effect of temperature on the activity and stability of amylase enzyme

Table 7.4: The values of absorbance optical density (OD) at four different temperatures (ͦ C).

No. Temperature (ͦ C) Absorbance Optical Density (OD) (nm)

0

0.0000002

0.0000004

0.0000006

0.0000008

0.000001

0.0000012

0.0000014

0.0000016

0.0000018

0 2 4 6 8 10

Enzyme

activity, V

(mol/min)

pH

A Graph of enzyme activity against pH



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1. 30 2.630

2. 40 5.350

3. 50 7.290

4. 60 8.070

The table 7.4 above showed the effect of four different temperatures on the reading of the

absorbance optical density (OD). The temperatures that required are in the range between 30 ͦ C

to 70 ͦ C only.

Figure 7.4: The reading of absorbance Optical Density (OD) (nm) against temperature (ͦ C)

The plotted graph in figure 7.4 showed the reading of absorbance Optical Density (OD) (nm) kept

increasing continuously against four different temperature which not exceed 70 ͦ C. The values of

absorbance Optical Density (OD) is more higher if the surrounding temperature not almost at

boiling temperature.

Table 7.5: The values of enzyme activity at four different temperatures

Temperature

(˚C)

Absorbance

reading (nm)

Glucose

concentration,

X (g/mL)

Glucose

released

(mol)

Enzyme

activity, V

(mol/min)

0

1

2

3

4

5

6

7

8

9

30 40 50 60 A b s o r b a n c e O p t i c a l D e n s i t y ( O D

)

( n m )

Temperature (ͦ

C)

A graph of absorbance Optical Density (OD) (nm) against

Temperature (ͦ

C)



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30 2.63 0.0015 8.33×10-6 8.33×10-7

40 5.32 0.0030 1.67×10-5 1.67×10-6

50 7.29 0.0041 2.28×10-5 2.28×10-6

60 8.07 0.0045 2.50×10-5 2.50×10-6

The table 7.5 above showed the effect of four different temperatures on the values of enzyme

activity for amylase enzyme.

Figure 7.5: The values of enzyme activity at four different temperatures

The graph that plotted as shown in the figure 7.5 showed the values of enzyme activity that

affected by the four different temperatures at range between 30 ͦ C to 70 ͦ C only. The values of

enzyme activity kept increasing as the enzyme is more reproducible under the optimum

temperature that not exceeds 70 ͦ C. The higher temperature at which the enzyme is operating at

is well above 100oC, and then thermal deactivation can occur which this condition also known as

denaturation.

The effect of substrate concentration on the activity of amylase enzyme

Table 7.6: The values of enzyme activity at different substrate concentration

0

0.0000005

0.000001

0.0000015

0.000002

0.0000025

0.000003

0 10 20 30 40 50 60 70

Enzyme

activity, V

(mol/min)

Temperature (˚C)

A Graph of Enzyme activity, V (mol/min)against Temperature

(˚C )



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Substrate

concentratio

n (%)

Absorbanc

e reading

(nm)

Glucose

concentration

, X (g/mL)

Glucose

released

(mol)

Enzyme

activity, V

(mol/min)

1/V 1/S

0.5 4.06 0.0023 12.27x10-6 12.27x10-7 8.15×105 2.00

1.5 3.39 0.0019 10.55x10-6 10.55x10-7 9.48×105 0.67

2.0 3.26 0.0018 9.991x10-6 9.991x10-7 1.00×105 0.50

2.5 2.66 0.0015 8.326x10-6 8.326x10-7 1.20×105 0.40

3.0 2.18 0.0012 6.661x10-6 6.661x10-7 1.50×105 0.33

The table 7.6 above showed the effect of five different substrate concentrations on the values of

enzyme activity for the amylase enzyme.

Figure 7.6: The values of enzyme activity against substrate concentration

Based on the observation, the graph that plotted in figure 7.6 showed the effects of substrate

concentration against the values of enzyme activity. The values kept decreasing since the amount

of substrate concentration kept increasing as well. This condition showed that the enzyme activity

a bit slow or being inhibited by the increasing of substrate concentration.

0

2

4

6

8

10

12

14

0 0.5 1 1.5 2 2.5 3 3.5 E n z y m e a c t i v i t

y ,

V ( m o l / m i n )

Substrate concentration (%)

Graph of enzyme activity against substrate concentration



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Figure 7.7: The values of 1/V that affected by the 1/S

Overall the graph that plotted in figure 7.7 showed the 1/S can affect the values of 1/V. Based on

the observation, the 1/V values were keeping decreased as the 1/S values were keeping longer.

The equation that being presented in this graph is = 3.8889 + 1.2327 and = 0.4161.

Calculation

1. Determination of glucose concentration, X (g/mL)

From the standard curve of glucose that had been plotted as shown in figure 7.1, the linear

equation of the curve is presented as:

= 0.0018

Where; X = protein concentration and Y = absorbance reading. Therefore, to calculate protein

concentration,

=

0.0018

=2.660

0.0018

=1477.78

×

1

1000

×1 × 1 0−

= 0.0015 g/mL

y = 3.8889x + 1.2327

R² = 0.4161

0

2

4

6

8

10

12

0.33 0.83 1.33 1.83 2.33

1/V

1/S

A Graph of 1/V against 1/S



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2. Determination of glucose released (mol)

MW of glucose = 180.1559 g/mol; Volume of enzyme (amylase) = 1 mL

Moles of glucose released (mol) = (

)

× ()

Moles of glucose released (mol) =0.0015

180.1559

× 1

Moles of glucose released (mol) = 8.326 × 10− mol

3. Determination of enzyme activity, V (mol/min)

Duration of hydrolysis reaction: 10 minutes

(/) =

(/) =8.326 × 10−

10

(/) = 8.326 × 10− mol/min

4. Equation for Michaelis-Menten:

=

[]

+

Double reciprocal;

1

=

1

+

1

=1

= 1

=1

=



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From graph, the linear equation obtained is:

= 3.8889 + 1.2327

Finding value of Vmax, maximum enzyme activity:

1

= 1.2327

= 0.8112 mol/min

Finding value of Km, Michaelis constant

= 3.8889

= (3.8889) × (0.8112) = 3.1547

Discussion

As the concentration of substrate increases, the rate of reaction also increases until the

point saturation occurs. It means as you increase the concentration, rate keeps increasing and

then one point comes when the maximum rate is achieved and there is no free enzyme to bind

with substrate and all the active sites of enzyme are bound to the substrate. So after that point,

increasing the concentration won’t have any effect. The maximum for each enzyme is usually

given by Km value (michealis menten graph or the other one called Lineweaver burke plot). The

Km value is the rate constant or it can be explained as how much substrate concentration is

required by an enzyme to reach to the half of maximum rate or velocity of enzyme. Each enzyme

has different Km values. Wherever the Vmax occurs and it intersects the curve drawn for substrate

concentration and velocity (or rate of reaction), that point is the saturation point or maximum

substrate concentration to have maximum rate of the reaction.

From the graph, we can see the results follow what is stated in theory. As the concentration

increase, the enzyme activity decrease. This is because when there is too much of substrate, theenzyme don’t have enough space to growth. So, to get optimum production of product, we need

to provide balance amount of substrate and enzyme

The enzyme reaction have effect with change of temperature. Based on the plotted graph,

as the temperature increase, the absorbance Optical Density (OD) also increase. Enzyme usually



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have its limit on temperature. When the temperature is very high, it will be denatured thus the

production of product decrease. From this experiment we can see that amylase enzyme still can

grow up to 60oC but the reaction of enzyme becomes slower. If this experiment is proceed with

higher temperature maybe the enzyme activity will decrease because starting from 50oC the

enzyme activity not have much increase. This is because the enzyme start to denatured.

pH can give several effect on structure and activity of an enzyme. For example, pH can

have an effect of the state of ionization of acidic or basic amino acids. Acidic amino acids

have carboxyl functional groups in their side chains. Basic amino acids have amine functional

groups in their side chains. If the state of ionization of amino acids in a protein is altered then the

ionic bonds that help to determine the 3-D shape of the protein can be altered. This can lead to

altered protein recognition or an enzyme might become inactive.

Changes in pH may not only affect the shape of an enzyme but it may also change the

shape or charge properties of the substrate so that either the substrate cannot bind to the active

site or it cannot undergo catalysis.

The most favorable pH value - the point where the enzyme is most active - is known as

the optimum pH.

Figure 9.1: Effect of pH on reaction rate (Anonymous, n.d)

In this experiment, the pH is increases from pH of 5 up to pH 9. But, starting from pH 6,

the enzyme activity decreases from 1.59×10-6 for pH 6 to 8.09×10-7 for pH 7. After that, the

enzyme activity decrease until pH 9 with value of 7.26×10 -7. Based on this result of experiment,

the optimum pH that is with highest velocity is sample pH 6 with velocity 0.2488. The lowest

velocity is pH 1.



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There is fluctuation of value of absorbance that give the fluctuation of value of velocity

might because of the sample is contaminated. The other factor might be the time for taking reading

of absorbance for every pH sample is not fixed. Besides that, while taking reading of absorbance,

the water vapor from condensation of the sample is still there, so, it might affect the absorbance

reading.

Conclusion

The data shown on the graph from the experiment shows that catalase functions of pH, substrate

concentration and temperature give different effect on enzyme activity. Table 7.3 shows that from

pH 5 to pH 6, the enzyme activity increases and at pH 7 the enzyme activity start to decrease.

The enzyme activity keep on decreasing when the pH is 8 and 9. When the enzyme activity

increase the absorbance reading also increase. By looking at figure 7.2 and figure 7.3, one cansee that as the pH of the solution rose to a pH of 6, catalase became more efficient and was able

to better carry out its function. These results help support the idea that as a solution becomes

more acidic than the optimum pH of an enzyme, the enzymes present in the solution will denature,

and in turn will not be able to function properly. This will result in lower reaction rates, which is

shown in figure 7.2 and 7.3.

At very high and very low temperatures we expected the absorbance or enzyme activity

be low. The highest absorbance should have appeared at room temperature, because most

human enzyme activity occurs at room temperature but in this case using enzyme amylase, westill cannot find the optimum temperature as we can see in figure 7.4 and figure 7.5 the graph did

not shows any decreasing in enzyme activity. For me I think maybe there is an error during

conducting experiment or maybe the amylase have high optimum temperature.

For the substrate concentration, we can see in figure 7.6 that as the percent of substrate

concentration increase, the enzyme activity increase.The information gathered throughout this

experiment is very useful for the future. This experiment has shown that enzymes must have

certain environmental conditions present in order for them to function properly. With this

knowledge, one can successfully perform experiments using enzymes in the future by makingsure that the environmental conditions present are optimum for the enzyme that is being used.

A limitation of the procedure was that we were unable to test for the presence of catalase

in the extract before beginning the experiment. If we were able to test for the presence of catalase

in the extract, we could have ensured that the decomposition of hydrogen peroxide resulted from

enzyme catalysis and not from the natural spontaneous decomposition of the chemical. Instead,



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we were forced to assume that catalase was present in the extract, an assumption that may, or

may not have, been correct.

Recommendations

This experiment must be carried out under the laminar flow hood for sterility to prevent

any contamination from the surrounding directly attached to the culture.

Properly, wash hand with plenty of water and appropriate soap after handling the culture

which can expose to the health.

Worn the appropriate gloves that provided and disinfect the work area with Ethanol (70%

ethanol for swabbing for sterility) before handling the culture.

Avoid the parallax error to be occurring during the measuring volume or amount of reagent

and solution by using provided apparatus. This can affect the concentration of solution

which indirectly interrupts the absorbance optical density (OD) values.

The amylase is easier to expose against the surrounding contaminants especially through

the air.

Always ensure the cuvette must be wiped cleanly to prevent any scratch that would affect

the spectrophotometer reading on absorbance optical density (OD).

Dispose of all contaminated materials after taking the reading of absorbance optical density

(OD) by using the spectrophotometer in appropriate containers.

Reference

Anonymous, (n.d). Effect of pH on enzyme. Retrieved on October 15, 2015

from http://academic.brooklyn.cuny.edu/biology/bio4fv/page/ph_and_.htm

David L. Nelson, Michael M. Cox , Lehninger principles of biochemistry, 4th edition.

vlab.amrita.edu,. (2011). Effect of Substrate Concentration on Enzyme Kinetics. Retrieved 15

October 2015, from vlab.amrita.edu/?sub=3&brch=64&sim=1090&cnt=1

Talamond, Pascale, Michel Noirot, and Alexandre De Kochko. “The Mechanism of Action of α-

amylase from Lactobacillus Fermentum on Maltooligosaccharides.”Journal of

Chromatography B (2005): 42-47. Science Direct . Web.

http://academic.brooklyn.cuny.edu/biology/bio4fv/page/ph_and_.htm

http://academic.brooklyn.cuny.edu/biology/bio4fv/page/ph_and_.htm



24

Appendix

Figure 12.1: Absorbance Optical Density

(OD) of Glucose

Figure 12.2: The effect of substrate

concentration

Figure 12.3: The effect of pH values Figure 12.4: The effect of temperature

Figure 12.5: Spectrophotometer Figure 12.6: Test tube



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investigation on enzyme activity and kinetics

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