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