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    nzymes

    ReactionDr. Yogi P. R.

    Biochemistry Department

    Medical Faculty

    Swadaya Gunung Jati University

    Cirebon 2009

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    Tujuan pembelajaran

    Untuk memahami dan mampu menjelaskan

    1.Pengertian, karakteristik, dan klasifikasi enzim

    2.Fungsi Enzim dalam regulasi reaksi kimiatubuh

    3.Faktor-faktor yang mempengaruhi kecepatan

    reaksi enzim dan regulasi aktifitas enzim4.Fungsi intraseluler melalui regulasi enzim

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    DEFINITION & CHARACTERISTIC

    Enzymes are :

    - Proteins

    - Metabolic catalysts

    - The largest and most highly specialized catalysts in the

    body for the reactions involved in metabolism whichincrease the rate of chemical reactions by lowering the

    activation energy of that reactions

    - Unchanged number of enzyme before and after reaction

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    E : Enzymes ES : Enzymes+Substrates

    S : Substrates P : Product

    ES low stability

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    Enzyme Function

    LOWERING ACTIVATION ENERGY

    9Menurunkan energi)

    THE FUNCTION OF CATALYST

    ENZYME IS A BIOCATALYST

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    Site of activity

    A. Endoenzyme

    Intracellular enzyme : ATP synthesis

    A. Eksoenzyme

    Extracellular enzyme

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    Catalysts effort

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    Occurred process

    A. Constitutive enzyme

    The number of enzyme always constant, not influence

    by substrate concentration (tdk berpengaruh olh cubstrat)

    A. Adaptive enzyme

    The occurred process is stimulated by substrate

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    STRUCTURE OF ENZYMES

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    Cofactor : Prostetic group

    Coenzyme Activator

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    COFACTOR COENZYMES

    Thiamine pyrophosphate, from Vit. B1, DecarboxylaseFlavin mono/adenine di nuceotide, Vit. B2, Dehydrogenase

    Nicatinamide Adenine Dinucleotide/ Phosphate, Nicotinicacid, Dehydrogenase

    Coenzyme A, Panthotenic acid, DehydrogenasePyridoxal phosphate, Vit. B6, Transferase

    Tetrahydrofolic, Folic acid, Transferase

    Deoxyadenosylcobalamine, Vit. B12, Isomerase

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    COFACTORS ACTIVATOR

    Fe2

    + orFe3

    + in Cytochrome oxidase,

    Catalase and Peroxidase

    Coin DinitrogenaseK+in Pyruvate kinase

    Mg+ in Glucose 6-phosphatase

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    Interaction Enzyme-Substrates Model

    Lock and key (1890 Emil Fischer)

    Stereospecificity catalysts

    The shape, or configuration, of the active site is especially

    designed for the specific substrate involved

    The configuration is determined by the amino acid sequence

    of the enzyme, the native configuration of the entire enzyme

    molecule must be intact for the active site to have the correct

    configurationThe substrate then fits into the active site of the enzyme in

    much the same way as a key fits into a lock

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    Induced fit (Daniel Koshland)

    The binding of a substrate (S) by an enzyme is an interactive

    process

    The shape of the enzyme's active site is actually modified

    upon binding S, in a process of dynamic recognition between

    enzyme and substrate called induced fit

    In essence, substrate binding alters the conformation of the

    protein, so that the protein and the substrate "fit" each other

    more precisely

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    Specificity Level of Enzymes

    1. Bond specificity (Low specificity)

    peptidase, phosphatase, esterase

    1. Group specificity (Middle specificity) hexokinase

    1. Absolute specificity (High specificity)

    urease

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    Velocity, Enzymes, Substrates

    Acceleration of product is determined by enzyme concentration and

    substrates concentration

    V = Velocity

    [E] = Enzyme concentration

    [S] = Substrates concentration

    A.If the S is CONSTANTThe increase of V is equal with the increase of E

    B.If the E is CONSTANT and S increase V will increase proportionally with

    the increase of S, but in higher concentration of S, the increasing of V willdecrease slowly until V was almost not suspended from S

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    A. B.

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    Michaelis Menten Model

    Leonor Michaelis & Maud Menten -1913

    Konstanta Michaelis-Menten Km = k2+k3/k1

    Km = The substrate at wich the velocity of the reaction is half the maximum

    velocityKm -- enzyme substrate complex high affinity

    Km -- enzyme substrate complex low affinity

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    Factors that influence enzymatic reaction

    1. Substrates

    the substrates concentration will enzymatic reaction

    until maximum condition

    1. pH

    optimum pH will enzymatic reaction

    example : Amilase -- optimum pH 5,0

    Arginase -- optimum pH 10

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    RateofR

    eactio

    n

    Substrate Concentration

    Substrate Concentration

    Active sites full- maximum turnover

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    Rateof R

    eaction

    pH

    1 3 42 5 6 7 8 9

    Narrow pH optima

    Disrupt Ionic bonds - Structure

    Effect charged residues at activesite

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    3. Temperature

    optimum temp will enzymatic reaction

    higher than optimum temp will damage enzyme

    ( 50C)

    If you heat the protein above its optimal

    temperature bonds break meaning the protein loses it

    secondary and tertiary structure

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    Effect of heat on enzyme activty

    Denaturing the protein

    ACTIVE SITE CHANGES SHAPE

    SO SUBSTRATE NO LONGER FITS

    Even if temperature lowered enzyme cant regain its correct shape

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    4. Inhibitor

    Competitive inhibitor Another substance (analog substrates) has similar structure to substrate

    Succinate Fumarate

    These compete with the substrate molecules for the active site

    Always reversible

    Increasing substrate concentration to against competitor

    SuccinateDehydrogenase

    Malonate

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    Non-Competitive inhibitor

    These are not influenced by the concentration of the substrate

    It inhibits by binding irreversibly to the enzyme but not at the active site

    Examples Cyanide combines with the Iron in the enzymes cytochrome oxidase

    Heavy metals, Ag orHg, combine withSH groups.

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    Feed-back inhibitor

    The first step (controlled by eA) is often controlled by the

    end product (F)

    Therefore negative feedback is possible

    A B C D E F

    The end products are controlling their own rate ofproduction

    eFeDeCeA eB

    Inhibition

    2008 Paul Billiet ODWS

    http://www.saburchill.com/IBbiology/bio_hp.htmlhttp://www.saburchill.com/IBbiology/bio_hp.html
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    Alosteric inhibitor

    These enzymes havetwo receptor sites

    One site fits thesubstrate like otherenzymes

    The other site fits aninhibitor molecule

    Inhibitor fits

    into allosteric

    site

    Substrate

    cannot fit

    into theactive site

    Inhibitor

    molecule

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    Five Main Ways that Enzyme Activity is Controlled

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    Five Main Ways that Enzyme Activity is Controlled

    in The Cell

    1. Enzyme production (transcription and translation of enzyme

    genes) enhanced or diminished by a cell in response to changesin the cell's environment

    This form ofgene regulation is called enzyme induction and inhibition. For

    example, bacteria may become resistant to antibiotics such as penicillin

    because enzymes called beta-lactamases are induced that hydrolyse the

    crucial beta-lactam ring within the penicillin molecule

    1. Enzymes can be compartmentalized, with different metabolic

    pathways occurring in different cellular compartments

    For example, fatty acids are synthesized by one set of enzymes in the cytosol,

    endoplasmic reticulum and the Golgi apparatus and used by a different set of

    enzymes as a source of energy in the mitochondrion, through -oxidation

    http://en.wikipedia.org/wiki/Transcription_%28genetics%29http://en.wikipedia.org/wiki/Translation_%28genetics%29http://en.wikipedia.org/wiki/Regulation_of_gene_expressionhttp://en.wikipedia.org/wiki/Enzyme_induction_and_inhibitionhttp://en.wikipedia.org/wiki/Antibiotic_resistancehttp://en.wikipedia.org/wiki/Penicillinhttp://en.wikipedia.org/wiki/Beta-lactamasehttp://en.wikipedia.org/wiki/Beta-lactamhttp://en.wikipedia.org/wiki/Cellular_compartmenthttp://en.wikipedia.org/wiki/Fatty_acidshttp://en.wikipedia.org/wiki/Cytosolhttp://en.wikipedia.org/wiki/Endoplasmic_reticulumhttp://en.wikipedia.org/wiki/Golgi_apparatushttp://en.wikipedia.org/wiki/Mitochondrionhttp://en.wikipedia.org/wiki/%CE%92-oxidationhttp://en.wikipedia.org/wiki/%CE%92-oxidationhttp://en.wikipedia.org/wiki/Mitochondrionhttp://en.wikipedia.org/wiki/Golgi_apparatushttp://en.wikipedia.org/wiki/Endoplasmic_reticulumhttp://en.wikipedia.org/wiki/Cytosolhttp://en.wikipedia.org/wiki/Fatty_acidshttp://en.wikipedia.org/wiki/Cellular_compartmenthttp://en.wikipedia.org/wiki/Beta-lactamhttp://en.wikipedia.org/wiki/Beta-lactamasehttp://en.wikipedia.org/wiki/Penicillinhttp://en.wikipedia.org/wiki/Antibiotic_resistancehttp://en.wikipedia.org/wiki/Enzyme_induction_and_inhibitionhttp://en.wikipedia.org/wiki/Regulation_of_gene_expressionhttp://en.wikipedia.org/wiki/Translation_%28genetics%29http://en.wikipedia.org/wiki/Transcription_%28genetics%29
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    3. Enzymes can be regulated by inhibitors and activators

    This helps allocate materials and energy economically, and prevents

    the manufacture of excess end products. The control of enzymatic

    action helps to maintain a stable internal environment in living

    organisms

    3. Some enzymes may become activated when localized to

    a different environment (eg. from a reducing (cytoplasm)

    to an oxidising (periplasm) environment, high pH to low pH

    etc).For example, hemagglutinin in the influenza virus is activated by a

    conformational change caused by the acidic conditions, these occur

    when it is taken up inside its host cell and enters the lysosome

    http://en.wikipedia.org/wiki/Enzyme_inhibitorhttp://en.wikipedia.org/wiki/Homeostasishttp://en.wikipedia.org/wiki/Cytoplasmhttp://en.wikipedia.org/wiki/Periplasmhttp://en.wikipedia.org/wiki/Hemagglutininhttp://en.wikipedia.org/wiki/Influenzahttp://en.wikipedia.org/wiki/Lysosomehttp://en.wikipedia.org/wiki/Lysosomehttp://en.wikipedia.org/wiki/Influenzahttp://en.wikipedia.org/wiki/Hemagglutininhttp://en.wikipedia.org/wiki/Periplasmhttp://en.wikipedia.org/wiki/Cytoplasmhttp://en.wikipedia.org/wiki/Homeostasishttp://en.wikipedia.org/wiki/Enzyme_inhibitor
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    5. Enzymes can be regulated through

    post-translational modification.

    For example, in the response to insulin, the phosphorylation of multiple

    enzymes, including glycogen synthase, helps control the synthesis or

    degradation ofglycogen and allows the cell to respond to changes in

    blood sugarAnother example of post-translational modification is Chymotrypsin, a

    digestive protease, is produced in inactive form as chymotrypsinogen in

    the pancreas and transported in this form to the stomach where it is

    activated. This stops the enzyme from digesting the pancreas or other

    tissues before it enters the gut. This type of inactive precursor to anenzyme is known as a zymogen.

    http://en.wikipedia.org/wiki/Post-translational_modificationhttp://en.wikipedia.org/wiki/Insulinhttp://en.wikipedia.org/wiki/Phosphorylationhttp://en.wikipedia.org/wiki/Glycogen_synthasehttp://en.wikipedia.org/wiki/Glycogenhttp://en.wikipedia.org/wiki/Blood_sugarhttp://en.wikipedia.org/wiki/Chymotrypsinhttp://en.wikipedia.org/wiki/Proteasehttp://en.wikipedia.org/wiki/Chymotrypsinogenhttp://en.wikipedia.org/wiki/Pancreashttp://en.wikipedia.org/wiki/Stomachhttp://en.wikipedia.org/wiki/Zymogenhttp://en.wikipedia.org/wiki/Zymogenhttp://en.wikipedia.org/wiki/Stomachhttp://en.wikipedia.org/wiki/Pancreashttp://en.wikipedia.org/wiki/Chymotrypsinogenhttp://en.wikipedia.org/wiki/Proteasehttp://en.wikipedia.org/wiki/Chymotrypsinhttp://en.wikipedia.org/wiki/Blood_sugarhttp://en.wikipedia.org/wiki/Glycogenhttp://en.wikipedia.org/wiki/Glycogen_synthasehttp://en.wikipedia.org/wiki/Phosphorylationhttp://en.wikipedia.org/wiki/Insulinhttp://en.wikipedia.org/wiki/Post-translational_modification
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    Thanks