Information about enzymes and how enzymes work.ppt

Enzyme

1. Enzymes Enzymes
The controller of all CHEMICAL The controller of all CHEMICAL
reactions in your bodyreactions in your body

2. Chemical Control (Enzymes)Chemical Control (Enzymes)
-at all times there are billions of chemical -at all times there are billions of chemical
reactions taking place in any organismreactions taking place in any organism
-all organisms therefore need to control these -all organisms therefore need to control these
chemical reactions that make up chemical reactions that make up metabolismmetabolism
--enzymesenzymes are the principal regulators of most are the principal regulators of most
chemical activity in living systemschemical activity in living systems
- - EnzymesEnzymes control chemical reactions and control chemical reactions and
therefore control therefore control MetabolismMetabolism
There are over 2000 known enzymes, each of There are over 2000 known enzymes, each of
which is involved with one specific chemical which is involved with one specific chemical
reactionreaction

3. EnzymesEnzymes

EnzymesEnzymes
- enzymes are proteins- enzymes are proteins
- enzymes are referred to as - enzymes are referred to as organic catalystsorganic catalysts

catalystscatalysts - inorganic or organic substance - inorganic or organic substance
which speeds up the rate of a chemical reaction which speeds up the rate of a chemical reaction
–Chemical reaction = Dehydration Synthesis and Chemical reaction = Dehydration Synthesis and
HydrolysisHydrolysis

activation energy - the energy that must be activation energy - the energy that must be
overcome in order for a overcome in order for a chemical reactionchemical reaction to to
occur. occur.
–Activation energy may otherwise be denoted as the Activation energy may otherwise be denoted as the
minimum energy necessary for a specific chemical minimum energy necessary for a specific chemical
reaction to occur. reaction to occur.

-- enzymes -- enzymes lower the energylower the energy needed to start a needed to start a
chemical rxn. (lower activation energy)chemical rxn. (lower activation energy)

4. reactants
products
e
n
e
r
g
y
Activation Energy
activation
energy, E
aa
transition state
(or activated complex)
bonds
breaking
bonds
forming
Course of reaction
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5. reactants
products
e
n
e
r
g
y
Intermediate
– formed
between
enzyme and
one or more
reactant
molecules
Uncatalysed
reaction
Enzyme-catalysed
reaction
Reaction profiles: uncatalysed and enzyme-catalysed
Click to see how an enzyme is involved in an enzyme-catalysed reaction
Course of reaction

6. StructureStructure

Structures of EnzymesStructures of Enzymes
- enzymes are large, complex proteins- enzymes are large, complex proteins
Protein Protein - all enzymes are either all protein or - all enzymes are either all protein or
are protein with non-protein parts called are protein with non-protein parts called
coenzymescoenzymes
- - coenzymescoenzymes are often vitamins are often vitamins
Composition of EnzymesComposition of Enzymes

apoenzymeapoenzyme -- protein part -- protein part

coenzyme coenzyme -- non-protein part attached to the -- non-protein part attached to the
main enzyme (usually a vitamin or a mineral) main enzyme (usually a vitamin or a mineral)

holoenzymeholoenzyme -- complete functional enzyme -- complete functional enzyme
(apoenzyme + coenzyme) (apoenzyme + coenzyme)

7. - ASE- ASE

Enzymes are named according to the Enzymes are named according to the
substratesubstrate they are specific to they are specific to
- substrates are the chemicals that each - substrates are the chemicals that each
enzyme acts uponenzyme acts upon
Example of Naming: Example of Naming:

The enzyme The enzyme maltase (enzyme)maltase (enzyme) breaks down breaks down
(acts upon) the dissaccharide (acts upon) the dissaccharide maltose maltose
(substrate) (substrate) into 2 monosacchardiesinto 2 monosacchardies

The enzyme peptidThe enzyme peptidasease breaks the peptide breaks the peptide
bonds in proteinsbonds in proteins

- Usually enzymes end in – - Usually enzymes end in – asease

8. Active Site or Binding SiteActive Site or Binding Site

Active Site or Binding Site Active Site or Binding Site
-enzymes are usually much bigger than -enzymes are usually much bigger than
their substratestheir substrates
-the protein chains fold to make a three -the protein chains fold to make a three
dimensional shape that has a specific dimensional shape that has a specific
pocket or pocket or sitesite where the substrate can where the substrate can
fit and interactfit and interact
-the specificity of the enzyme is -the specificity of the enzyme is
dependent upon its dependent upon its active siteactive site

9. Enzyme Enzyme
Holoenzyme
Chemical RXN
occurring
ACTIVE SITE

10. ““Lock and Key Theory”Lock and Key Theory”

"Lock and Key Theory" "Lock and Key Theory"
-- each enzyme is specific for one and ONLY -- each enzyme is specific for one and ONLY
one substrate (one lock - one key) one substrate (one lock - one key)

It is thought that, in order for an enzyme to It is thought that, in order for an enzyme to
affect the rate of a reaction, the following affect the rate of a reaction, the following
events must take place.events must take place.

11. Enzyme Substrate ComplexEnzyme Substrate Complex
1. Enzyme forms a temporary association with 1. Enzyme forms a temporary association with
the substrate or substratesthe substrate or substrates
2. The Enzyme and Substrate form a close 2. The Enzyme and Substrate form a close
physical association between the molecules physical association between the molecules
called an called an enzyme substrate complexenzyme substrate complex
3. While the 3. While the enzyme substrate complex enzyme substrate complex is is
formed, the enzyme action takes place and formed, the enzyme action takes place and
the substrate is broken down into its smaller, the substrate is broken down into its smaller,
simpler parts (Example: a dissacharide simpler parts (Example: a dissacharide
becomes 2 monosaccharide or 2 becomes 2 monosaccharide or 2
monosacchardies become a disaccharde) monosacchardies become a disaccharde)
4. After completion, the enzyme and the 4. After completion, the enzyme and the
products separate. The enzyme is then ready products separate. The enzyme is then ready
to react with another substrate.to react with another substrate.

12. Enzyme – Substrate ComplexEnzyme – Substrate Complex

13. Note: Enzymes do eventually wear out, so they have to be synthesized
by the cells and replaced.
-enzymes are not changed during reactions and therefore can be reused

14. reactant 1
+
reactant 2
products
e
n
e
r
g
y
Intermediate :
enzyme/reactant 1
+
reactant 2
no enzyme
present
enzyme
present
+
enzyme
+
enzyme
Course of reaction
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15. New Enzymes New Enzymes

** Although enzymes may be reused in ** Although enzymes may be reused in
cells, they eventually are destroyed and cells, they eventually are destroyed and
new ones must be synthesized. new ones must be synthesized.

-- begin to be destroyed above 45 C. -- begin to be destroyed above 45 C.
(above this temperature all proteins (above this temperature all proteins
begin to be destroyed) begin to be destroyed)

16. Factors Influencing Rate of Factors Influencing Rate of
Enzyme Action Enzyme Action

1. pH - the optimum (best) in most living things is close to 7 1. pH - the optimum (best) in most living things is close to 7
(neutral) -- high or low pH levels usually slow enzyme activity (neutral) -- high or low pH levels usually slow enzyme activity

A few enzymes (such as gastric peptidase) work best at a pH of A few enzymes (such as gastric peptidase) work best at a pH of
about 2.0 about 2.0

2. Temperature - strongly influences enzyme activity 2. Temperature - strongly influences enzyme activity
- optimum temperature for maximum enzyme function is - optimum temperature for maximum enzyme function is
usually about 35-40 C. usually about 35-40 C.
-- reactions proceed slowly below optimal temperatures -- reactions proceed slowly below optimal temperatures
-- above 45 C. most enzymes are destroyed -- above 45 C. most enzymes are destroyed

3. Concentrations of Enzyme and Substrate 3. Concentrations of Enzyme and Substrate

** When there is a fixed amount of enzyme and an excess of ** When there is a fixed amount of enzyme and an excess of
substrate molecules -- the rate of reaction will increase to a substrate molecules -- the rate of reaction will increase to a
point and then level off. point and then level off.

** This leveling off occurs because all of the enzyme is used up ** This leveling off occurs because all of the enzyme is used up
and the excess substrate has nothing to combine with. and the excess substrate has nothing to combine with.

-- If more enzyme is available than substrate, a similar rx. rate -- If more enzyme is available than substrate, a similar rx. rate
increase and leveling off will occur. (The excess enzyme will increase and leveling off will occur. (The excess enzyme will
eventually run out of substrate molecules to react with.) eventually run out of substrate molecules to react with.)