BIOKIMIA ENZIM

ENZYMES Pendahuluan (overview) Enzyme Specificity Kofaktor Enzim Enzyme Nomenclature Lock and Key

Enzyme-Substrate Complex Induced Fit Theory

Cara Kerja Enzim Conditions Affecting the Actions of Enzymes Inhibitor Enzim Isozim/Isoenzim Regulation of Enzymatic Activity

PENDAHULUAN

Organisme hidup rangkaian reaksi biokimia peran enzim

Enzim : biokatalisator yg mengatur kecepatan berlangsungnya semua proses fisiologis

Hampir semua dr 2000/ lebih enzim yg diketahui merupakan protein globular

Aktivitas katalitiknya bergantung pd integritas struktur sbg protein

Contoh : Jika enzim dididihkan dg asam

kuat/diinkubasi dg tripsin (perlakuan yg memotong rantai polipeptida) aktivitas katalitiknya akan hancur pentingnya struktur kerangka primer protein enzim

Jika struktur berlipatnya rantai protein yang khas dr enzim diubah (oleh panas, pH extrim, senyawa perusak ) aktivitas katalitiknya juga lenyap jadi struktur primer, sekunder dan tertier protein juga penting bagiaktivitas katalitiknya.

KESPESIFIKAN ENZIM

Enzymes are highly specific both in the reactions they catalyze and in the compounds (reactants/substrates)

on which they actContoh : enzim proteolitikMengkatalisis hidrolosis ikatan peptidaEnzim2 proteolitik berbeda tingkat

spesifisitas substratnya, misalnya : SUBTILIN pd bakteri tdk bedakan ik. peptida yg akan

diputus TRIPSIN ik. pep pd sisi karboksil arginin/lisin TROMBIN ik.pep antara arginin dan glisin

KOFAKTOR ENZIM Dlm fungsinya sbg katalisator suatu reaksi

kadang enzim cukup mengandalkan struktur proteinnya, tp. kadang enzim butuh senyawa lain yang bukan protein yang disebut KOFAKTOR

Yg termsk kofaktor : ION LOGAM MAUPUN SUATU MOLEKUL ORGANIK

KOMPLEKS YG DISBT KOENZIM KOENZIM/GUGUS YG MEMBENTUK IKATAN

KOVALEN DG ENZIM DISBT SBG GUGUS PROSTETIK.

Kompleks enzim-kofaktor disebut Holoenzim,Jikakofaktornya diambil, disebut Apoenzim

ENZYMES Enzymes are PROTEIN CATALYSTS

Large complex proteins made up of one or more polypeptide chains

In Vivo called an enzyme. Outside the body it is just called a catalyst

Control the rate of chemical reactions that take place in cells, tissues, and organs. Each chemical reaction that occurs in a living system

requires the assistance of a specific enzyme Catalyst: A substance that changes the speed

of a chemical reaction without itself undergoing a permanent chemical change in the process

OVERVIEW

In a chemical reaction, reactants collide and enter into a transition state this state is short and

rapidly breaks down to either products or reactants

Free energy (G) Free Energy of

Activation ( G ) Free Energy

difference ( G)

WHAT IS HAPPENING... Catalyst reduces amount of activation

energy so the reaction occurs faster Catalyst accelerates both the forward and

reverse reactions and thus only increases the rate at which a reaction approaches equilibrium

EndoenzymeFound and used within the cell

ExoenzymeSecreted into extracellular environment

later taken up by the cells for use

ENZYME NOMENCLATURE The official name of an enzyme has TWO (2)

parts First: names the substrates or the products of the

reaction Second: Designates the type of reaction

catalyzed

CLASSES OF ENZYMES

NAMING AND CLASSIFICATION Enzymes can be classified by chemical

reaction catalyzed1. Addition/Removal of water

a) Hydrolase - carbohydrase, amidase,

proteaseb) Hydrase

-fumarase, enolase, carbonic anhydrase

2. Transfer of electrons

a) Oxidase

b) Dehydrogenase

3. Transfer of a radical

a) Transglycosidase - monosaccharides

b) Transphosphrylase & Phosphomutase- phosphate group

c) Transaminase - amino groupd) Transmethylase - methyl groupe) Transacetylase - acetyl group

4. Splitting of forming a C-C bonda) Desmolase

5. Changing geometry or structure of moleculea) Isomerase

6. Joining two molecules through hydrolysis of pyrophosphate bond in ATP of tri-phosphatea) Ligase

“LOCK AND KEY” THEORY “Lock and Key” theory: simple analogy commonly

used to explain the specificity of enzymes A specific key will only open a specific lock

The key can be used over and over on the same type of lock

ENZYME-SUBSTRATE COMPLEX Explains the specificity of enzyme action Substrates of an enzymatic reaction bind to a

specific site on the enzymeshape of that site is complementary to that of the substrates

Active Site: part of an enzyme to which the substrates bind (most cases: a pocket of groove in the surface of the protein) Included within the pocket are functional

groups that attract the substrate molecules and mediate the catalytic event

ENZYME-SUBSTRATE COMPLEX DRAWING

EXAMPLES OF ACTIVE SITES

INDUCED FIT THEORY Active site on enzyme

not as rigid as “lock and key” model

As the substrate attaches to the enzyme’s active site, the site changes shape to fit the substrate improves the fit of the

active site to the substrate

brings catalytic groups into the correct position for action

MECHANISMS OF CATALYSIS A large part of the catalytic power of an

enzyme depends on its ability to lower the activation energy

To do so, an enzyme may provide an environment within the active site that favors the transitions state...or it may provide catalytic groups that allow the reaction to proceed via intermediates not part of the uncatalyzed reactionmany enzymes act as general acid-

base catalysts

MECHANISMS OF CATALYSIS

Polypeptides cannot by themselves catalyze all of the biologically important reactions. Use coenzymes and cofactors

COFACTORS / COENZYMES Cofactors:

non-protein component of enzymesrequired for the enzyme to function inorganic

Coenzymes: like a cofactor, but organicfound mostly in vitamins

Both cofactors and coenzymes make up part of the active site

COENZYMES Interacts with the active site of the enzyme

and acts as a catalytic group in the reaction some are permanently attached

either covalently or non covalently Each type of coenzyme is specialized to

perform one of a small number of biochemical functions but may perform that same function for more than one enzyme

BIOTIN: EXAMPLE OF COENZYME Serves as the

coenzyme for several enzymes

one of the 9 water-soluble vitamins required by humans

Example:pyruviate

carboxylase acetyl-CoA

carboxylase both catalyze the

fixation of Co2

CONDITIONS AFFECTING THE ACTIONS OF ENZYMES Heavy Metal Ions Temperature pH salt Amount of Substrate concentration

*everything that affect a protein affect an enzyme because ENZYMES ARE PROTIENS

HEAVY METAL IONS

Can disrupt enzymatic activity when present at active site, substitution of a

different metal ion for the original ion causes the enzyme to malfunction and denature

EXTREMES OF TEMPERATURE Changes enzyme structure

changes active site prevents enzyme from

attaching to substrate The thermal agitation of

the enzyme molecule disrupts the hydrogen bonds, ionic bonds, and other weak interactions within the protein molecule

In humans, enzymes have an optimum temperature of 37ºC

PH CHANGES ON ENZYME ACTIVITY Extreme changes in pH

values denature such ionisable enzymes rendering them ineffective within a narrow pH range,

enzyme structure changes reversibility, and each such enzyme was optimally at a specific pH

Optimal pH values for most enzymes 6-8 pH exception: I.e. digestive

enzymes in stomachs

INHIBITORS

Competitive InhibitorsCompete with substrate for the enzymesDo not affect VmaxRaise the apparent Km

NONCOMPETITIVE INHIBITORS

Do not affect Km Lower Vmax Slows down dissociation of ES

ENZYMES IN BIOTECHNOLOGY

Biotechnology is the application and harnessing of microorganisms (such as bacteria, viruses and fungi) or biological processes to produce desired and useful substances and facilitate industrial processes.

FERMENTATION: EXAMPLE OF BIOTECHNOLOGY Ex: The manufacture of wine, involves

the fermentation of grape juice, a rich source of glucose, by wild yeasts present on grape skinfermentation of sugar by yeast is the basis

for the production of other alcoholic drinks Better brewing through improving

yeast and large scale production are the results of biotechnologygenes responsible for the yeast enzymes

have been cloned and bacteria has been used in large scale production of the yeast enzymes needed

GENETIC ENGINEERING

Involves the manipulation of genes used to describe the modern techniques in

molecular biology where genes can be removed from one type of a cell to another, altering a cell’s properties

USED IN: producing new antibodies, insulin, and biological detergents

BIOLOGICAL DETERGENTLipolase: enzyme which is constituent

of biological detergents, consists of fat-digesting (splitting) enzymes

Widely used in the soap and detergent industrysave energyrapidly biodegradable, thus leaving no

harmful residuesno negative impact on sewage

treatment processespose no risk to aquatic life

STREPTOKINASE IN BREAKING DOWN BLOOD CLOTS STREPTOKINASE

can dissolve blood clots that form in the heart, blood vessels, or lungs after a process, such as a heart attack

called a thrombolytic agent can also dissolve blood clots that form in

intravenous catheters tubing that goes into a vein for fluid exchange