Salivary Amylase

Activity of Salivary Amylase Amylase Domingo, Guray, Hugo, Lorenzo, Mohammad Isa

Intro Because everything has a start

Catalysis

 The process of increasing the rate of reaction with the use of a catalyst.

 Catalyst – any substance that increases rate of reaction upon addition to

a certain reaction

Enzymes

 Act on substrates in a reaction  Highly specific  Breaks down complex macromolecules, synthesizes compounds

essential for the cell  Active site  Enzyme-substrate complex  Speeds up reaction rates

Enzymes

 Require cofactors for activity  Classified according to the types of reaction r eaction they catalyze

– Oxidoreductase – Transferase – Hydrolase – Lyase – Isomerase – Ligase

Amylase

 An enzyme that breaks down starch into oligosaccharides through

hydrolysis  Secreted by the human’s parotid glands and the pancreas  α-Amylase  β-Amylase  γ-Amylase

Factors that may affect catalysis rates

 Temperature  pH  Enzyme concentration  Amount of substrate

Materials and Methods

Solution Preparation

Saliva was collected.

1 ml of saliva was diluted to 10 ml with distilled water.

 10 % salivary amylase solution

Estimation of salivary amylase activity

A mixture of 5.0 mL 1% starch, 2 mL 1% NaCl solution and 2 mL

phosphate buffer put in a test tube and then placed in a water bath At 38oC, 1 mL salivary enzyme solution added to the solution. A drop from the digestion mixture mixed with 1 drop d rop of iodine for every

minute.  Achromic point was determined.

Effect of enzyme concentration

The salivary amylase solution diluted to five lower concentrations: 2.5%,

2.0%, 1.5%, 1.0%, 0.75% and 0.5%.  The same procedure done as previous using 1% concentration of starch

solution. Reaction rates observed for each dilution.

Effect of amount of substrate

 Six percent starch prepared from which five other dilutions were

prepared: 5%, 4%, 3%, 2%, and 1%. The same procedure for Estimation of salivary amylase activity used

using 2.5% salivary amylase solution. Reaction rates for each substrate dilution recorded.

Effect of pH

A mixture of 0.2 M sodium biphosphate (Na 2HPO4) and 0.1 M citric acid

prepared to obtain different buffer solutions with pH varying from 3.0 to 8.0. Similarly, procedures from the estimation of enzymatic activity were

applied, recording all notable reaction rates for each pH setup.

Effect of temperature

Test tube with 2.5% salivary enzyme was placed on water baths

maintained at 4 oC, 10oC, 38oC, 58oC, 78oC and 100 oC.  Reaction rates recorded.

Results and Discussion

Estimation of amylase activity

 Achromic point is the time it takes for

the enzyme to completely hydrolyze the starch solution.  enzyme-starch mixture is not able to

produce a blue to violet color with iodine -> absence of starch

Estimation of amylase activity Table1. Effect of Enzyme Concentration on the Rate of Reaction. Different Dilutions of Saliva and Their Corresponding Time to Reach the Achromic Points, Amylase Units and Enzyme Activity Effect of Enzyme Concentration Salivary Amylase (%) 0.5 0.75 1 1.5 2 2.5

time to achromic point (min)

amylase units

Enzyme activity

30

0 .8 3 3 3 3 3 3 3 3

0.4000

1.630434783

0.2667

2 .7 7 7 7 7 7 7 7 8

0.2000

6 .8 1 8 1 8 1 8 1 8

0.1333

14.28571429

0.1000

17.85714286

0.0800

23

18

11

7

7

Amylase units - amount of enzyme necessary to digest 5 ml 1% starch to reach the achromic point within 10 minutes

Effect of Enzyme Concentration

enzyme + substrate <=> enzyme-substrate complex <=> enzyme + product

Effect of Enzyme Concentration Table1. Effect of Enzyme Concentration on the Rate of Reaction. Different Dilutions of S aliva and Their Corresponding Time to Reach the Achromic Points, A mylase Units and Enzyme Activity Effect of Enzyme Concentration Salivary Amylase (%)

time ime to achromi omic point int (min min)

0.5

30

0.75

23

1

18

1.5

11

2

7

2.5

7

amylas lase units

Enzyme activi ivity

0.833333333

0.4000

1.630434783

0.2667

2.777777778

0.2000

6 .8 1 8 1 8 1 8 1 8

0 .1 3 3 3

14.28571429

0 .1 0 0 0

17.85714286

0.0800


Increased enzyme concentration increases reaction rate (more enzymes en zymes are present to act upon a fixed amount of substrate)

However, as substrate concentration is constant, it produces a limiting effect on reaction rate rate (excess enzymes enzymes begin to compete for substrate)

Surplus of enzymes on a limited reaction rate causes overall enzyme activity to diminish (reaction rate cannot cope up with increased enzyme conc)


Effect of the Amount of Substrate

 Rate of Reaction

– describes how fast a chemical reaction proceeds – depends on reactant and product concentrations • More importantly on rate constant k


 Enzyme Kinetics

– still follows the same trend • Increasing either substrate or enzyme increases rate – but there is a limit to this relation • When enzyme conc are constant, there is a limit to the velocity velocity of the reaction


 Michaelis-Menten Kinetics

– enzymatic reactions are observed to reach a maximum rate of reaction Vmax – constant enzyme concentration provides a limiting effect • All enzymes are bound to substrate –

= Vmax [S] / (Km + [S])

v o


 Rectangular Hyperbola  Max rate of Vmax  Half-Velocity is reached

at Km  Vmax is dependent on

[E}  Km is constant

– Km=K-1 + K2 / K+1.

Rate of Reaction vs. Substrate Concentration Rate increases with substrate concentration However exponential relation Due to experiment limit (30 min)

Rate of Reaction vs. Substrate Concentration Allowing time to go beyond 30, rectangular hyperbola is attained Change in rate diminishes as substrate conc increases


 Asymptotical nature makes it hard to determine which much certainty the

values of Km and Vmax  Algebraic manipulation (double-reciprocal plot) allows linear expression of

MM eq.  Lineweaver-Burke Equation

– : 1/v = (Km / Vmax) (1/ [S]) + (1/Vmax) o


 Linear equation  Regression Analysis

allows determination of Km and Vmax  Also able to determine

nature of protein function inhibition (competitive, uncompetitive, noncompetitive)

Double Reciprocal Plot Not strong liinear relation (due to experimental limits) R2 value of only 0.785

Double Reciprocal Plot Perfect linear relation Vmax= 2.08333E-05

Km=4.16667E-05

Very Low Km, high affinity of enzyme

Effect of pH

• Enzymes are proteins – function is ultimately determined by their structure

• optimal pH range – Changes in pH • excess of either H+ or OH- ions • affect the secondary, tertiary and quarternary structures by disrupting hydrogen bonds and van der wal interactions. • change the active site of the enzymes – preventing the enzymatic reaction

Effect of pH

• Enzymes – have a range of pH at which it is active and outside of which it is inert – optimum pH • most favorable pH value • point where the enzyme is most active • extremely high or low pH values generally result in complete loss of activity for most enzymes

• Salivary amylase has an optimum pH of around 7

Effect of pH

Figure5. Effect of Varying pH in Enzymatic Activity of

Effect of pH

 enzymatic activity of salivary amylase is highest at pH 7

– pH of oral cavity is close to 7  At pH 8,

– decrease in activity  acidic pH 3, 4 and 5

– enzyme acitivity was at minimum

Effect of Temperature

• reaction rate of an enzymatic reaction increases as the temperature is raised • 10° C rise in temperature will increase the activity of most enzymes by 50 to 100% • many enzymes are adversely affected by high temperatures – Reaction rates may increase with temperature up to a maximum level, but then abruptly decline with further increase of temperature

• increases in temperature are able to break H-bonds and van der wal interactions


 decrease in temperature, rate of reaction is decreased due to lowered

energy  over a period of time, enzymes will be deactivated d eactivated at even moderate

temperatures  most enzymes lose activity at 5°C and when frozen


Figure6. Effect of Varying temperature in Enzymatic activity.


• highest enzyme activity was seen in the temperature 38°C – near temperature in the oral cavity

• other temperature levels – enzyme activity was found to be minimal – achromic point was not reached r eached within the 30min limit

• optimum enzyme activity is at that level closest to the natural physiological setting • high heat – denaturation

• very low temperatures – lowered chemical kinetics

Conclusion

 1 ml of human saliva has around 17.86 Units of amylase.  Increased enzyme concentration increases reaction rate, however, it

decreases overall enzyme activity.  Increased substrate concentration increases reaction rate, however there

is a maximum rate that can be achieved. (Vmax)  Michaelis-Menten and Lineweaver-Burke describes enzyme kinetics. The

Michaelis constant Km gives an idea on enzyme affinity.  Salivary amylase has a Km = 4.84e-4 (corrected: 4.167e-5)  There is an optimal pH and temperature range for enzyme activity.

Outside this range, enzyme activity drastically decreases due to denaturation and deactivation.  Optimal pH would be near 7 while optimal temperature should be near 37

Thank you!! 

Salivary Amylase

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