1. ENZIM 2014

52
1 Enz Enz i i m m

description

mata kuliah enzim

Transcript of 1. ENZIM 2014

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EnzEnziimm

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PENDAHULUAN

Reaksi kimia dalam sel

membutuhkan katalisis spesifik

MAKANAN DICERNA dalam saluran pencernaan

DIMETABOLISME dalam sel

ENZIMSEL JARINGAN ORGANISME

tersusun dari molekul2

REAKSI KIMIA

EnzEnziim m 1)Merupakan molekul yang besar sebagai – protein (biokatalisator) yg lebih besar dari substrat

2) mempunyai Active site – daerah yang spesifik berinteraksi dg substrat.

KATALISATOR mempercepat reaksiIkut serta dalam reaksi kimia & mempercepat reaksi kimia, tetapi pada akhir reaksi akan didapat kembali seperti semulaDibutuhkan dalam jumlah kecil

Mechanisms of Catalysis

Metal Ion or =Organic Molecule

= OrganicCofactor

Polypeptide

KOFAKTOR BERUPASENYAWA ORGANIKNON PROTEIN YG.

SPESIFIK

BAGIAN PROTEIN dari ENZIMJK. SENDIRIAN TIDAK AKTIF

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ALUR METABOLIK

A = substrat awal P = produk akhir B,C,D,E,F,G = senyawa2 antara

(intermediates) E1 searah

A BE1

CE2 D

E3E

E4 FE5

GE6

PE7

E. regulator

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LETAK ENZIM DALAM SEL Berkaitan dengan fungsi organel yang bersangkutan E. Mitokondrial reaksi pengadaan energi

Reaksi oksidasi energiRantai respirasi dalam

mitokondria E. Ribosomal sintesis protein

Enz

yme

Loca

lizat

ion

Organization of Electron Transport Chain of Cellular Respiration: Substrate Enzyme Product Enzyme chains are co-localized

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KATALISATOR INORGANIK

1. H+, OH-, Pt

2. E. aktivasi 3. -4. -

ENZIM

Bio katalisator

1. Protein biokatalisator

2. E aktivasi 3. Bereaksi spesifik4. Tidak tahan

panas

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Ea

Ea'

Ea''

Perjalananreaksi

E.

leve

lG

E. bebas

kead. transisi

tanpa katalisator

dgn katalisator inorg

dgn enzim

G = PerubahanE. bebas

kead. awal

kead. akhir

C6H12O6 + O2

CO2 + H2O + E

Che

mic

al R

eact

ion

Note no change in degree of spontaneity, i.e., in G

Thermodynamics

Che

mic

al R

eact

ion

Activa

tion

Energ

y

ActivationEnergy

a.k.a., Substrateif enzyme catalyzed

Cat

alyz

ed R

eact

ion

At a given temperature catalyzed Rxns can run faster because less energy is required to achieve the transition state

Cat

alyz

ed R

eact

ion

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Keadaan awal pd suhu tertentuReaksi kimia : A PA+B C+DΔG = 0 seimbangΔG < 0 Rx ke kanan bersifat

eksergonikΔG > 0 Rx ke kanan bersifat

endergonik

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Ea = ENERGI AKTIVASIJumlah energi yg diperlukan untuk membawa

semua molekul dalam 1 mole suatu bahan pd suatu suhu tertentu dari keadaan awal menuju keadaan transisi

Mengatasi hambatan energiΔG : perubahan energi bebas

Tidak dipengaruhi katalisatorENZIM BEREAKSI SPESIFIK artinya :

Suatu enzim hanya dapat bereaksi dengan suatu substrat tertentu atau pada atau pada sejumlah kecil senyawa sejenis

Contoh : Laktosa glukosa + galaktosa Heksokinase :- Glukosa

- Heksosa lain: fruktosaDaya ikat (afinitasnya) beda lihat KM

Laktase

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Kekhususan enzim K. Absolut K. Relatif K. Optik maltase K. Gugus alkohol dehidrogenase

Dipengaruhi oleh: Ikatan E-S Sifat gugus katalitik Kofaktor

A + B C2 A + 2 B 2 C3 A + 3 B 3 CE / Kat tidak berhubungan secara stoikiometrik dengan reaktan / produk

E

active site

S

x

3x

2x

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KELAS-KELAS ENZIM MENURUT IUBMB

ADA 6 KELAS (GOLONGAN) UTAMA :1. OKSIDOREDUKTASE :

MENGKATALISIS REAKSI OKSIDASI – REDUKSI.P.U. : ENZIM2 PD. PROSES OKSIDASI BIOLOGIS

PIRUVAT + NADH + H+ LAKTAT + NAD+

2. TRANSFERASE : MENGKATALISIS TRANSFER/PEMINDAHAN GUGUS

FUNGSIONAL (BUKAN HIDROGEN) ANTARA SEPASANG SUBSTRAT

S–G + S’ S’–G + S

-D-GLUKOSA+ATP -DGLUKOSA-6-P +ADP

3. HIDROLASE : MENGKATALISIS PEMBELAHAN HIDROLITIKContoh : Enzim - Amilase

- Lipase- Karboksi peptidase A

Reaksi:-D-GALAKTOSIDA + H2O = suatu alkohol + D-galaktosa

Laktat dehidrogenase

Mg++

HeksokinaseGlukokinase

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KELAS-KELAS ENZIM MENURUT IUBMB

4. LIASE (LYASE) : MENGKATALISIS REAKSI PEMBENTUKAN ATAU PEMECAHAN

IKATAN RANGKAP DUA, ATAU PEMBELAHAN LAIN YG. MENYANGKUT PENYUSUNAN KEMBALI ELEKTRON

Contoh : ALDOLASE : KETOSA-I-P ALDOSA + DIHIDROKSI ASETON-P

FUMARASE : HO – CH – COOH H – C – COOH | ==== || + H2O CH2 – COOH HOOC – C – H

MALAT FUMARAT

PIRUVAT DEKARBOKSILASE : O O || ||– OOC – C – CH3 + H+ CO2 + H – C – CH3

PIRUVAT ASETALDEHID

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KELAS-KELAS ENZIM MENURUT IUBMB

5. ISOMERASE : MENGKATALISIS PENYUSUNAN KEMBALI INTRAMOLEKULERAll Trans – retinin 11 – cis – retinin

6. LIGASE : MENGGABUNGKAN 2 MOLEKUL, DISERTAI PEMUTUSAN

IKATAN PIROFOSFAT PADA ATP ATAU SENYAWA SEJENISMis : ~ PIRUVAT KARBOKSILASE : O O || || – OOC – C – CH3

+ CO2 – OOC – C – CH2 – COO –

ATP ADP+PiPIRUVAT OKSALOASETAT

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STRUKTUR PROTEIN

H O H O H O H | || | || | || |+H3N – C – C – N – C – C – N – C – C – – – N – C – C | | | | | | | R1 H R2 H R3 H R

IKATAN PEPTIDA

||

O

|O–

ujungkarboksil bebasujung

amino bebas

H |R – C – COOH | NH2

asam amino

»

• ASAM AMINO DALAM LARUTAN SELALU BERMUATAN• PROTEIN JUGA SELALU BERMUATAN

»aa1 aa2

aa3 aa4 aa5 aa6

COO–+H3N

RANTAI PEPTIDA 20 jenis a.a. dasar

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STRUKTUR PRIMER PROTEIN :

URUTAN ASAM AMINO PD. RANTAI PEPTIDA DR. UJUNGAMINO BEBAS SAMPAI UJUNG KARBOKSIL BEBAS

(awal) (akhir)

URUTAN a.aJUMLAH a.a

letak ujung NH3+

letak ujung –COOH–

letak suatu a.a

H |R – C – COOH | NH3

+

H |R – C – COO–

| NH3

++H+

H |R – C – COO–

| NH2

+OH–

pH < iep iepmuatan=0

pH>ieppKa COOH < NH3

+

PD. TIAP JENIS RANTAI PROTEIN TIDAK SAMA (BERBEDA)

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STRUKTUR SEKUNDER :

H H O | | ||– N – C – C – | CH2

| S | S | CH2

|– N – C – C – | | || H H O

ikatandisulfida

R | C – C – N – || | | O H H : : : : : : : : H H O | | ||– N – C – C | R

ikatan Hidrogen

* Lain2 : * LIPIT = - PLEATED * KUMPARAN ACAK = RANDOM COIL

Cys– SH

Cys– SH

* Helix

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STRUKTUR TERSIER :

E

celahaktif

Dari satu untai rantai polipeptida monomer

- Contoh : MIOGLOBIN (MYOGLOBINE) MONOMER- Struktur Tersier :

• IKATAN HIDROGEN• GAYA2 VAN DER WAALS IKATAN2 YG. LEMAH

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STRUKTUR KUARTERNER :

MONOMER

PROTOMER

DIMER

TETRAMER

OLIGOMER

POLIMER

subunit

subunit

TERMASUK STRUKTURKUARTERNER

T.D. SATU UNTAI RANTAI POLIPEPTIDA

HANYA SAMPAI STRUKTUR TERSIER

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STRUKTUR KUARTERNER :

SATU MOLEKUL T.D. > 1 RANTAI PEPTIDA

T.D. 2 SUBUNIT ATAU LEBIH 1 SUBUNIT ~ 1 RANTAI PEPTIDA

DIIKAT OLEH : IKATAN HIDROGEN IKATAN ELEKTROSTATIK

KEGUNAAN : SUPAYA MOLEKULNYA LEBIH STABIL UNTUK MENDAPAT FUNGSI TERTENTU

ENZIM

IKATAN2 YGLEMAH

CELAH AKTIF(ACTIVE SITE)

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~ PH/PH, t DENATURASI

POLIMER~ T.D. BANYAK SUBUNIT(BANYAK RANTAI POLIPEPTIDA)

~ : DIMER

: TETRAMER

OLIGOMER

4 RANTAI POLIPEPTIDA4 SUBUNIT

~ PROTEIN :- ENZIM FUNGSIONAL- KOLAGEN STRUKTURAL

~ IKATAN PEPTIDAIKATAN DISULFIDAIKATAN YG. KUAT, TIDAK RUSAK

STRUKTUR PROTEIN RUSAK, TP. TIDAK SAMPAI MERUSAK STRUKTUR PRIMER

ikt peptida

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CARA KERJA ENZIM

SE

+

celah aktif = celah katalitik= celah pengikat substrat

KompleksE - S

+P

E

~

E : ENZIMS : SUBSTRATP : PRODUK

~ UKURAN MOLEKUL E : BESARUKURAN MOLEKUL S : KECIL

~ DALAM SISTEM BIOLOGIS : KADAR E << KADAR SUBSTRAT

~ IKATAN E–S IKATAN YG, LEMAH

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KEKHUSUSAN ENZIM

BILA ADA KESESUAIAN ANTARA CELAH AKTIF DGN. SUBSTRAT PD. STRUKTUR 3 DIMENSINYA MAUPUN GUGUS REAKTIF YG. DIMILIKI KEDUANYA.

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TEORI KUNCI & ANAK KUNCI FISHER

TEORI KESESUAIAN IMBAS (KOSHLAND)

PENGIKATAN S PERUBAHAN KONFORMASI(SUSUNAN ATOM DLM RUANG)

• BENTUK BERPASANGAN TERJADI SETELAH E MENGIKAT S

The Lock and Key Hypothesis

Enzyme may be used again

Enzyme-substrate complex

E

S

P

E

E

P

Reaction coordinate© 2007 Paul Billiet ODWS

Induced fit model

Diagrams to show the induced fit hypothesis of enzyme action.

FAKTOR-FAKTOR YANG MEMPENGARUHI KERJA ENZIM

KADAR ENZIMKADAR SUBSTRATpHSUHUEFEKTOR :

EFEKTOR POSITIF = AKTIVATOREFEKTOR NEGATIF = INHIBITOR

Substrate concentration: Non-enzymic reactions

The increase in velocity is proportional to the substrate concentration

Reaction velocity

Substrate concentration

© 2007 Paul Billiet ODWS

Substrate concentration: Enzymic reactions

Faster reaction but it reaches a saturation point when all the enzyme molecules are occupied.If you alter the concentration of the enzyme then Vmax will change too.

Reaction velocity

Substrate concentration

Vmax

© 2007 Paul Billiet ODWS

The effect of pH

Optimum pH values

Enzyme activity Trypsin

Pepsin

pH1 3 5 7 9 11

© 2007 Paul Billiet ODWS

pH OPTIMUM UMUMNYA BERKISAR ANTARA pH 5 – 9 (BERBENTUK GENTA)PERKECUALIAN: MISALNYA PEPSIN pH OPTIMUMNYA 1-2

Ak

rivi

tas

E (

%)

100

pH < pH opt pH>

The effect of pH

Extreme pH levels will produce denaturation

The structure of the enzyme is changed

The active site is distorted and the substrate molecules will no longer fit in it

At pH values slightly different from the enzyme’s optimum value, small changes in the charges of the enzyme and it’s substrate molecules will occur

This change in ionisation will affect the binding of the substrate with the active site.

© 2007 Paul Billiet ODWS

The effect of temperature

Q10 (the temperature coefficient) = the increase in reaction rate with a 10°C rise in temperature.For chemical reactions the Q10 = 2 to 3(the rate of the reaction doubles or triples with every 10°C rise in temperature)Enzyme-controlled reactions follow this rule as they are chemical reactionsBUT at high temperatures proteins denatureThe optimum temperature for an enzyme controlled reaction will be a balance between the Q10 and denaturation.

© 2007 Paul Billiet ODWS

PENGARUH SUHU PD AKTIVITAS ENZIM

SUHU ENERGI KINETIK REAKSI LEBIH CEPAT

ENZIM ADALAH PROTEIN MAKIN MUDAH DENATURASI

t

o

o

P

50o C

60o C

40o C

80o C

t1 t2

The effect of temperature

Temperature / °C

Enzyme activity

0 10

20

30

40

50

Q10 Denaturation

© 2007 Paul Billiet ODWS

The effect of temperature

For most enzymes the optimum temperature is about 30°C

Many are a lot lower, cold water fish will die at 30°C because their enzymes denature

A few bacteria have enzymes that can withstand very high temperatures up to 100°C

Most enzymes however are fully denatured at 70°C

© 2007 Paul Billiet ODWS

Inhibitors

Inhibitors are chemicals that reduce the rate of enzymic reactions.

The are usually specific and they work at low concentrations.

They block the enzyme but they do not usually destroy it.

Many drugs and poisons are inhibitors of enzymes in the nervous system.

© 2007 Paul Billiet ODWS

Inhibition

Competitive inhibitors bind reversibly to the enzyme.

STRUKTUR INHIBITOR KOMPETITIF

INHIBITOR KOMPETITIF YANG KLASIK

STRUKTUR I MIRIP S I ANALOG S.

I BEREBUT DANGAN S UNTUK MENEMPATI

CELAH AKTIF ENZIM

I

S

E

I

More-Subtle Inhibition of Active Sites (1/2)

Mor

e-S

ubtle

Inhi

bitio

n (2

/2)

The effect of enzyme inhibition

Irreversible inhibitors: Combine with the functional groups of the amino acids in the active site, irreversibly.

Examples: nerve gases and pesticides, containing organophosphorus, combine with serine residues in the enzyme acetylcholine esterase.

© 2007 Paul Billiet ODWS

The effect of enzyme inhibition

Reversible inhibitors: These can be washed out of the solution of enzyme by dialysis.

There are two categories.

© 2007 Paul Billiet ODWS

The effect of enzyme inhibition

2. Non-competitive: 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 or Hg, combine with –SH groups.

These can be removed by using a chelating agent such as EDTA.

© 2007 Paul Billiet ODWS

Applications of inhibitors

Negative feedback: end point or end product inhibition

Poisons snake bite, plant alkaloids and nerve gases.

Medicine antibiotics, sulphonamides, sedatives and stimulants

© 2007 Paul Billiet ODWS