enzyme kinetics and associated reactor design: introduction to enzymes,

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Prof. R. Shanthini 23 Se Enzyme kinetics and associated reactor design: Introduction to enzymes, enzyme catalyzed reactions and simple enzyme kinetics CP504 – Lecture 3 learn about enzymes learn about enzyme catalyzed reactions study the kinetics of simple enzyme catalyzed react

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CP504 – Lecture 3. Enzyme kinetics and associated reactor design: Introduction to enzymes, enzyme catalyzed reactions and simple enzyme kinetics. learn about enzymes learn about enzyme catalyzed reactions study the kinetics of simple enzyme catalyzed reactions. What is an Enzyme?. - PowerPoint PPT Presentation

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Page 1: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

Enzyme kinetics and associated reactor design:

Introduction to enzymes, enzyme catalyzed reactions and

simple enzyme kinetics

CP504 – Lecture 3

- learn about enzymes

- learn about enzyme catalyzed reactions

- study the kinetics of simple enzyme catalyzed reactions

Page 2: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

What is an Enzyme?

Enzymes are mostly proteins, and hence they consists of amino acids.

Enzymes are present in all living cells, where they help converting nutrients into energy and fresh cell material.

Enzymes breakdown of food materials into simpler compounds.

Examples: - pepsin, trypsin and peptidases break down proteins

into amino acids - lipases split fats into glycerol and fatty acids- amylases break down starch into simple sugars

Page 3: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

Enzymes are very efficient (biological) catalysts.

Enzyme catalytic function is very specific and effective.

Enzymes bind temporarily to one or more of the reactants of the reaction they catalyze.

By that means, they lower the amount of activation energy needed and thus speed up the reaction.

Enzymes does not get consumed in the reaction that it catalyses.

What is an Enzyme?

Page 4: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

Oxidoreductase: transfer oxygen atoms or electron

Transferase: transfer a group (amine, phosphate, aldehyde,

oxo, sulphur, etc)

Hydrolase: hydrolysis

Lyase: transfer non-hydrolytic group from substrate

Isomerase: isomerazion reactions

Ligase: bonds synthesis, using energy from ATPs

Enzyme classification

Page 5: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

Examples of Enzyme Catalysed Reactions

CO2+ H2O H2CO3 Carbonic anhydrase

Carbonic anhydrase is found in red blood cells.

It catalyzes the above reaction enabling red blood cells to transport carbon dioxide from the tissues (high CO2) to the lungs (low CO2).

One molecule of carbonic anhydrase can process millions of molecules of CO2 per second.

Example 1:

Examples of enzyme catalyzed reactions

Page 6: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

2H2O2 2H2O + O2 Catalase

Catalase is found abundantly in the liver and in the red blood cells.

One molecule of catalase can breakdown millions of molecules of hydrogen peroxide per second.

Hydrogen peroxide is a by-product of many normal metabolic processes.

It is a powerful oxidizing agent and is potentially damaging to cells which must be quickly converted into less dangerous substances.

Example 2:

Examples of enzyme catalyzed reactions

Page 7: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

- in the food industry for removing hydrogen peroxide from milk prior to cheese production

- in food-wrappers to prevent food from oxidizing

- in the textile industry to remove hydrogen peroxide from fabrics to make sure the material is peroxide-free

- to decompose the hydrogen peroxide which is used (in some cases) to disinfect the contact lens

Industrial use of catalase

Page 8: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

See the hand out on the same topic

Examples of Industrial Enzymes

Page 9: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

Enzymes are very specific.

Absolute specificity - the enzyme will catalyze only one reaction

Group specificity - the enzyme will act only on molecules that have specific functional groups, such as amino, phosphate or methyl groups

Linkage specificity - the enzyme will act on a particular type of chemical bond regardless of the rest of the molecular structure

Stereochemical specificity - the enzyme will act on a particular steric or optical isomer

More on enzymes

Page 10: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

Source: http://waynesword.palomar.edu/molecu1.htm

Page 11: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

Source: http://waynesword.palomar.edu/molecu1.htm

E + S ES

Page 12: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

Source: http://waynesword.palomar.edu/molecu1.htm

Lock & Key Theory Of Enzyme Specificity(postulated in 1894 by Emil Fischer)

E + S ES E + P

Page 13: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

Page 14: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

Active Site Of Enzyme Blocked By Poison Molecule

Source: http://waynesword.palomar.edu/molecu1.htm

Page 15: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

Induced Fit Model(postulated in 1958 by Daniel Koshland )

Source: http://www.mun.ca/biology/scarr/Induced-Fit_Model.html

Binding of the first substrate induces a conformational shift that helps binding of the second substrate with far lower energy than otherwise required. When catalysis is complete, the product is released, and the enzyme returns to its uninduced state.

E + S ES E + P

Page 16: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

E + S ES E + Pk1

k2

k3

which is equivalent to

S

P[E]

S for substrate (reactant)

E for enzyme

ES for enzyme-substrate complex

P for product

Simple Enzyme Kinetics

Page 17: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

Michaelis-Menten approach to the rate equation:

Assumptions:

1. Product releasing step is slower and it determines the reaction rate

2. ES forming reaction is at equilibrium

3. Conservation of mass (CE0 = CE + CES)

E + S ES E + Pk1

k2

k3

Initial concentration of E

Concentration of E at time t

Concentration of ES at time t

Page 18: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

Michaelis-Menten approach to the rate equation:

E + S ES E + Pk1

k2

k3

rP = - rS = k3 CES

Product formation (= substrate utilization) rate:

k1 CE CS = k2 CES

Since ES forming reaction is at equilibrium, we get

(1)

(2)

Page 19: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

Michaelis-Menten approach to the rate equation:

E + S ES E + Pk1

k2

k3

k1 (CE0 – CES) CS = k2 CES

Using CE0 = CE + CES in (2) to eliminate CE, we get

which is rearranged to give

CE0CSCES = k2/k1 + CS

(3)

Page 20: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

Michaelis-Menten approach to the rate equation:

E + S ES E + Pk1

k2

k3

k3CE0CSrP =

rmaxCS = KM + CS

(4)

Using (3) in (1), we get

k2/k1 + CS

- rS =

where rmax = k3CE0

and KM = k2 / k1 (6)

(5)

Page 21: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

Assumptions:

1. Steady-state of the intermediate complex ES

2. Conservation of mass (CE0 = CE + CES)

E + S ES E + Pk1

k2

k3

Initial concentration of E

Concentration of E at time t

Concentration of ES at time t

Briggs-Haldane approach to the rate equation:

Page 22: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

E + S ES E + Pk1

k2

k3

Briggs-Haldane approach to the rate equation:

rP = k3 CES

Product formation rate:

(7)

rs = - k1 CECS + k2 CES

Substrate utilization rate:

(8)

k1 CECS = k2 CES + k3 CES

Since steady-state of the intermediate complex ES is assumed, we get

(9)

Page 23: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

E + S ES E + Pk1

k2

k3

Briggs-Haldane approach to the rate equation:

rP = - rS = k3 CES

Combining (7), (8) and (9), we get

(10)

k1 (CE0 - CES)CS = (k2 + k3)CES

Using CE0 = CE + CES in (9) to eliminate CE, we get

which is rearranged to give

CE0CSCES = (k2+k3)/k1 + CS

(11)

Page 24: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

E + S ES E + Pk1

k2

k3

Briggs-Haldane approach to the rate equation:

where rmax = k3CE0

and KM = (k2 + k3) / k1(13)

Combining (10) and (11), we get

k3CE0CS- rS =(k2+k3)/k1 +CS

rmaxCS =

KM + CS

(5)

(12)rP =

When k3 << k2 (i.e. product forming step is slow),

KM = k2 / k1(6)

Page 25: Enzyme kinetics and associated reactor design: Introduction to enzymes,

Prof. R. Shanthini 23 Sept 2011

where rmax = k3CE0 and KM = f(rate constants)

- rS rmaxCS =

KM + CS rP =

Simple Enzyme Kinetics (in summary)

S

P[E]

rmax is proportional to the initial concentration of the enzyme

KM is a constant