enzymes power point part 1 %28webct%29
TRANSCRIPT
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1. Introduction2. Cofactor3. Specificity of Enzyme
4. Naming / Nomenclature5. Classification of Enzyme6. Enzyme Kinetic & Michaelis-
Menten equation7. Factor affect enzyme activity
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Majority biochemical reaction cant take place spontaneously
Enzyme - Introduction
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Metabolism is usually divided into two
categories: Catabolism breaks down organic matter, for
example to get energy in cellular respiration. Anabolism uses energy to construct
components of cells such as proteins and
nucleic acids.
Enzyme - Introduction
Biochemical reaction
http://en.wikipedia.org/wiki/Catabolismhttp://en.wikipedia.org/wiki/Cellular_respirationhttp://en.wikipedia.org/wiki/Anabolismhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Nucleic_acidhttp://en.wikipedia.org/wiki/Nucleic_acidhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Anabolismhttp://en.wikipedia.org/wiki/Cellular_respirationhttp://en.wikipedia.org/wiki/Catabolism -
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Chemical reaction Using catalyst rate (acceleration) of chemical
reaction Catalyst - remain unchanges
Enzyme - Introduction
Majority biochemical reaction cant take place spontaneously
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What is enzyme? In biochemical reaction Catalyst enzymesExample: Oxidation of fatty acid
Break down of protein
Enzyme - Introduction
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Oxidation of fatty acid
The oxidation of a fatty acid to carbon dioxide andwater is not a gentle process in a test tube -
extremes of pH, high temperatures and corrosivechemicals are required.
Yet in the body, such a reaction takes placesmoothly and rapidly within a narrow range of pH
and temperature.
Enzyme - Introduction
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Break down of protein
In the laboratory, the average protein mustbe boiled for about 24 hours in a 20% HCl
solution to achieve a complete breakdown.
In the body, the breakdown takes place infour hours or less under conditions of mild
physiological temperature and pH.
Enzyme - Introduction
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Enzymes: Protein in nature High molecular weight
~ 10,000 to 2,000,000 Chain of amino acid Linked by peptide bond Denature at high temperature
Precipitated with salts / solvent
Enzyme Chemical Nature
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Enzyme
posses catalytic activity
rate of chemical reactionNo changes in the reactionRegenerate afterward
Enzyme Chemical Nature
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Cell metabolism required:
1. Extracting matter & energy from
the environment2. transporting various chemicals3. synthesizing new biomolecules
4. moving within its environment5. replicating, new generation
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Without enzymes very slowly or no reaction enzymes speed up reactions
maintain their life each reaction within cell catalyzed by a specific enzyme
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Enzymes - Protein in nature
3o structure
Folding rule Polar out / Non-polar InBonding
1. Hydrophobic interaction2. H-bond3. Ion pair (salt bridges)
4. Disulfide bonds
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What is substrate?
In enzymatic reaction
Substrate beginning of the process
Within substrate make / break chemical bonds
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Enzyme active site
Polypeptide chain folded unique 3-D shape pocket or cleft on the enzyme
surface active site
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substrate binds to the active site ofthe enzyme
form an Enzyme-Substrate complex
(ES complex) further reactions & form product then regenerated enzyme
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enzyme molecule lock Substrate key, active site keyhole of the lock.
This description is called the lock-and - key theory of enzymestructure.
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Some enzymes-Required NO chemical groups foractivity
Some enzymes- Require additional chemicalcomponent
- addition component Cofactor
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Three types of cofactors
Nature: organic or inorganic
Cofactor:**Non Protein chemical component**
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1.Coenzymecofactor enzyme loosely bound
Non-protein organic substanceAs carriers for transferring chemicalgroups or atoms from one enzyme toanotherMany coenzymes are derived fromvitamins
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1.Coenzyme
Example:
Nicotinamine adenine dinucledtide (NAD)acts as a coenzyme to dehydrogenase(the enzyme)by acting as a hydrogenacceptor
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2.Prosthetic groupcofactor enzymetightly bound
covalent bond
Non-protein organic molecules
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2.Prosthetic group
Example:
Haem is a prosthetic group.It is a ring-shaped organic molecule withiron at its centre.Haem is the prosthetic group of theelectron carrier cytochrome and of the enzyme catalase.
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Three types of cofactorsNature: organic or organic
3.Metal ions / inorganic ionsvarious metal ione.g. Mg+2, Mn+2, Zn+2, Cu+2
enzyme metalloenzymes
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3.Metal ions / inorganic ions
Example:Salivary amylaserequires thepresence of chloride (Cl-) ions beforeit will efficiently change starch intomaltose
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Apoenzyme an enzyme requires cofactor but does not have bound
Inactive enzyme
Holoenzyme
an apoenzyme + cofactor catalytically active
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Active site (key hole)
Specific 3 dimensional shape
Only one type of substrate
Specificity
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Few enzymesabsolute specificityCatalyze only one particular reaction
Other enzymesSpecificity for particular chemical
bond / functional group
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4 main classes of specificity :
1.Absolute specificity
2.Group specificity
3.Linkage specificity
4.Stereospecificity
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Enzyme only catalyse on onereaction
Example1. succinate dehydrogenase, that is specific for
succinate (In citric acid cycle / Krebs cycle)
1. Absolute specificity
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enzyme act on substrate which substrate with specific functional groups
ExamplePhosphatases
phosphate functional group
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enzyme only act on substrate which substrate having particular type of chemical bond /
linkage
Example
Esterases - hydrolysis of esters
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enzyme only act on substrate which substrate having steric / optical isomer
Example: Enzyme can discriminate between D-
stereoisomers and L-stereoisomers Catalyse the reaction on one of them
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Example: (a) & (b) are stereoisomer
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How polypeptide chain folds &make the active site
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1. -ve charged amino acid enzymeve charged substrate +ve charged Electrostatic interaction
e.g. aspartic acid & glutamic acid
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2. +ve charged amino acid Enzyme +ve charged Substrate -ve charged Electrostatic interaction E.g. histidine, lysine and arginine
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4. Hydrophilic amino acid Enzymehydrophilic Substratehydrophilic Hydrogen bonding
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Simple naming system
1. According to substrate that the
enzyme acted on Added suffix -ase
For example, Enzyme acted on substrate - arginine
called arginase
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Simple naming system
2. According to the type of reaction
catalyzed Added suffix -ase
For example, Enzyme glucose oxidase catalyzes
oxidation of glucose
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Systematize naming enzyme
International Enzyme Commission
IEC
based on type of catalytic reaction
6 major categories
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1. Oxidoreductases catalyze oxidation-
reduction reactionsExample:
Oxidoreductases - require a cofactor
NAD+, which accepts the hydrogens released during oxidation.
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1. Oxidoreductases catalyze oxidation-
reduction reactionsExample:
Oxidases - oxygen is used as an acceptor
glucose oxidase, glucose gluconic acid
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2. Transferases catalyze - transfer
functional groups of substrateExample:methyltransferase, transfers a methyl group
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2. Transferases catalyze - transfer
functional groups of substrateExample:transaminase, transferring an amino functional group from one
molecule to another. This allows for the interconversion of certainamino acids, and also allows amino acids to enter into glucosemetabolism.
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3.Hydrolases catalyzeaddition of a water moleculeprocess called hydrationcleaves the bond
Example:
Lipases, phosphatases,acetylcholinesterase and proteases
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4. Lyases catalyze removal of various groups from substrates
forming double bonds cleavage of C-C, C-O and C-N bonds not by means of hydrolysis
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5. Isomerases catalyze intramolecular rearrangements E.g. interconversion of D &L-isomeric
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6. Ligases catalyze the formation ofchemical bonds.
E.g. C-C, C-S, C-O and C-N bond
need input of chemical energy, ATPto form new bond
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