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8/9/2019 Dinh Nghia Phan Loai

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Unit 3. nh ngha v phn loi enzyme, cc yu t

nh h-ng n hot tnh ca enzyme v ng hcenzyme

3.1 nh ngha v phn loi enzyme3.2 Cc tnh cht ca enzyme3.3 Cc yu t nh h-ng (to, pH, [E,S], ion,cofactor, inhibitor)

3.4 C ch c ch enzyme


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* Enzymes : All enzymes are protein in nature that areproduced by living cells to serve as biological catalysts.

* iu khin hu ht cc phn ng ha hc trong t bo sng

(E. colic 4288 protein, trong c 2656 -c xc nh

cc c tnh v trong s xc nh c 64%

(1701) l enzyme)

Enzyme l g ?


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C cht l cht hoc cc cht m phn ng

enzyme xc tc.

Trung tm xc tc (active site) l mt b phn

c bit ca enzyme c cht bn vo trong

qu trnh phn ng.

Cc thut ng v nh ngha enzyme


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Cofactor: cc ion hu c nh v hu ht cc ion kimloi: Cu, Mg, Mn, hot ng nh- cht kch hot hocc ch

Coenzyme : cc ligand nh kh ng phi l protein(cofactor hu c) xc tc phn ng cho & nhn cc int, chuyn nhm, ph v hoc hnh thnh lin kt.

Vitamin : acscorbate, cyanocobalamin, folic acid,etc

Apoenzyme l mt b phn protein ca enzyme.


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Cc cofactor lin kt cht -c gi lprosthetic group (holoenzyme = enzyme

+ cofactor, apoenzyme = enzyme khuyt

cofator) Bt k phn t no lin kt vi enzyme

-c gi l ligand (bao gm c c cht v

cht nh h-ng)


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The cofactors and coenzymesMetal ions cofactors

Metal ions EnzymesCa+2 Pancreatic lipaseCu+2 Ascorbic acid oxidase, monamine

oxidase, cytochrome oxidaseFe+2 Catalase and cytochromes

Mg+2 KinasesMn+2 Arginase, phosphatase, carboxylaseZn+2 Carboxypeptidase, carbonic anhydraseMo+2 Xanthine oxidase


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Coenzyme Reaction Catalyzed

Biotin Carboxylation

Cobalamin (B12) Alkylation transferCoenzyme A Acyl transfersFlavin Oxido-ReductionLipoic acid Acyl transfersNicotinamide Oxido-Reduction

Pyridoxal phosphate Amino group transfersTetrahydrofolate One carbon grouptransfersThiamine pyrophosphate Aldehyde transfer

Common Coenzymes


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Vitamin B complex coenzymes

Enzymes Coenzyme Vitamins

dehydrogenases Thiamine(B1) TPPFMN, FAD dehydrogenases Riboflavin (B2)dehydrogenasesNAD, NADP Niacin (nicotinic acid)PPTransaminase, Pyridoxine (B6)

CoASH Pyruvate dehydrogenase Pantothenic acidThiokinaseThymidylic acids ynthetase FH4 Folic acidCobamides phenylalanine, hydrolase, B12


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Cofactors or Coenzymes


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S kch hot enzyme: bt k qu trnh no mkhi ng hoc lm tng tnh hot ng ca

enzyme.

S c ch enzyme: bt k qu trnh no lm choenzyme lm gim tnh hot ng hoc c ch.

Cht c ch cnh tranh (Competitive inhibitor):

bt k cht no m lin kt vi trung tm hot

ng ca enzyme lm ngn nga s lin kt c

cht.



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* S iu ho ng-c (Feedback) l qu

trnh iu ho enzyme m sn

phm ca hng lot cc phn ng xc tc

c ch phn ng tr-c theo trnh t.

S iu ho enzyme & Feedback


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Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings

c chng- c (Feedbackinhibition)

Cc yu t nh h- ng n ho t tnh enzyme

Figure 5.8


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Cht c ch kh ng cnh tranh (Noncompetitiveinhibitor): bt k cht no m lin kt vi mt phn caenzyme ngoi trung tm hot ng m c ch hottnh ca enzyme.

Tnh hoat ng ca enzyme (Enzyme Activity) l

mt s o vn tc ca phn ng tng ln bao nhiu khic s hin din ca enzyme.



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1 n v hot tnh (unit activity) l mt l-ng

protein cn thit chuyn ho 1 Qmole c cht

trn 1 pht nhit ti -u & pH ti -u

1 n v hot ring (unit SPECIFIC ACTIVITY) ltng s n v trn mg protein c mt

1 n v hot phn t (unit MOLECULAR

ACTIVITY) l tng s n v trn Qmole enzyme

tinh ch

nh ngha tnh hot ng ca enzyme


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I. Lc xc tc

N lm tng tc ca phn ng ln n hng

1000 ln

N hot ng nhit va phi v pH trung

tnh (Enzyme t archeabacteria l ngoi l)

(V d c bit l c nh nit (N2thnh

ammonia)

700 ~ 900K, 100 ~ 900atm vi cht xc tc st.

nitrogenase l 300K, pH trung tnh, 1atm vi st

v molybden)

1.3 Cc tnh cht ca enzyme


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1.3. Cc tnh cht ca enzyme

I. Hiu qu xc tc (Catalytic efficiency)

Hu ht cc phn ng xc tc enzyme chiu qu cao, n xy ra nhanh hn ccphn ng khng xc tc t 103 n 108 ln.Mi phn t enzyme c kh nng chuynha 100 n 1000 phn t c cht thnh

sn phm trong mt giy.


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2. Tnh c tr-ng

Hu ht cc enzyme hon ton hoc gn

nh- hon ton c c tr-ng vi c cht

* Mt s enzyme phn ng vi mt di rng

c cht l peptidase, phosphatase, esterase

(lin kt c tr-ng), v hexokinase (nhmc tr-ng)


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a- Hon ton c trng: enzyme ch lin kt vi mt loi ccht.VD glucokinase ln glucose, arginase ln arginine,sucrase ln sucrose.

b- c trng cu to (group): enzyme c trng vi ccnhm (groups) hoc cc nguyn t xung quang lin kt.Dovy n s hot ng nn nhm nh ca c cht relatedsubstrates e.g.Trypsin c trng vi lit kt peptide c carboxyl group

ca cc amino acid baz nhng khng c trng vi aminoacids pha khc ca lin kt.Chemotrypsin c trng vi lin kt peptide c carboxylgroup ca amino acid thm.


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*Enzyme nhn bit chn lc c cht ring*Tnh c trng c kim sot bi cu to

enzyme kim sot tnh chn lc c cht v snphm.

Tnh c trng


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Enzyme lin quan ti kiu c cht

Enzyme c tnh c trng cao i vi loi phn ng xctc, nhng n khng phi lc no cng ng vi c cht mchng xc tc

succinic dehydrogenase thng xc tc phn ng xy hakh v c cht ca n l succinic acid alcohol dehydrogenase thng xc tc cc phn ng xy hakh nhng n xc tc nhiu loi alcohol(ru cn) khc nhau. Enzymes cn c trng chung cho cu trc steric ring

(optical isomer) ca c cht tr racemase xc tc c 2 dng ccht D & L


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Enzyme c tnh c trng c cht

Khi c cht lin kt vi enzyme, enzyme xc tcchuyn i c cht thnh sn phm. Sucrase l enzyme lin kt vi sucrose v ph v

disaccharide thnh fructose v glucose.


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c- Tnh c trng tng i: l c trng vi lin kt, vvy m enzyme hot ng nn cc c cht ln e.g. lipase,dipeptidase (c trng vi lin kt peptide gia 2 amino

bt k).

d- Tnh c trng quang hc: Nu c cc ng phn,enzyme s lin kt vi ch mt dng e.g. L-amino acidoxidase ch hot ng nn L- amino acid nhng khng nn

D amino acid.


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c tr-ng kh ng gian (Stereospecific)

* Dehydrogenase vi NAD+ or NADP+

* Phn ng ch vi mt thnh phnx-ng sng (chiral compound)

( S chnh xc c th nhn bit -ctrong DNA/RNA polymerase v trong

tng hp protein)


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3. S iu ho (Regulation) Hot tnh ca enzyme c th c iu ha bng skch hot hoc c ch tc to thnh sn phm png nhu cu ca t bo.

* Cc hot tnh enzyme -c iu ho bi cc ionnh hoc cc cht nh h-ng nh (effectors), nh-phosphate hoc Ca 2+

* S iu ho -c th ng qua s thay i cu trc

ho tr* S c ch phn hi (Feedback) th-ng trongnhiu chu trnh sinh tng hp enzyme



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1.4 Cofactors

Nhiu enzyme, nh- chemotrypsin v

triosephosphate isomerase, kh ng cn b

sung yu t ph tr.

Nhiu enzyme khc i hi thnh phn

non-protein cho hot tnh enzyme.

Cc cht ph tr ion kim loi v hu c(th-ng l cc dn xut t B vitamin) l cc

nhm chnh ca cofactor


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1.5.2 Isoenzyme

Trong cc loi ring bit, c nhiu hnmt dng enzyme c th xc tc cng mtphn ng (1 SCD chut, 2 ng-i, 3

chut cng) Khc nhau trnh t, cofactor, v cutrc

in di (Electrophoresi) th-ng -cdng phn loi


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Isoenzymes

Isoenzymes hoc isozymes l nhng enzyme xc tc cngmt phn ng nhng chng c cc tnh cht vt l khcnhau nh electrophoretic mobility, immunogenicity etc.Bi v chng khc bit v trnh t amino acid.

Isoenzymes c th c nhiu amino acid mang in tch v

c th tch bng in di.


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Multienzyme

Mt enzyme c nhiu hn mt hot tnh xctc

N c th c nhiu hn mt s phn loi EC


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Vn tc phn ng:

S thay i nng c cht ban u hoc sn phmcui cng ca phn ng trn mt n v thi gian.

Turnover number:S phn t c cht chuyn i thnh sn phm trnmt phn t enzyme trn giy.


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1.5 nh danh enzyme

Mt s tn gi enzyme kh ng lin quan g tivic hnh thnh phn ng xc tc, eg. catalase,

trypsin, papain .

IUBMB (International Union of Biochemistryv

Molecular Biology) -c thnh lp vo nm1955


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CCH TTN ENZYME:

1-Thm ui ase sau tn c cht. e.g lactase, arginase. Thyphn lactose v arginine.

2- Thm hot ng ca enzyme vo tn c cht, e.g malatedehydrogenase (loi hidro t malate), glutathione reductase(kh glutathione).

3- Mt s enzyme cn gi tn c, e.g pepsin, trypsin. etc.


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PHN LOI ENZYME


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Enzyme c th phn loi theo cc phn ngha hc m n xc tc

1. Oxidoreductases oxidation/reduction (eg. dehydrogenases)2. Transferases group transfer (eg. kinases)3. Hydrolases hydrolysis (eg. proteases)4. Lyases lysis, generating double bond (eg. synthases)5. Isomerases rearrangement (eg. racemases)

6. Ligases ligation requiring ATP (eg. synthetases)


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Oxidoreductase

1.1 Hot ng ln nhm CH-OH

1.2 Hot ng ln nhm aldehydehoc oxo

1.3 Hot ng ln nhm CH-CH1.4 Hot ng ln nhm CH-NH2

1.n.1 NAD(P) nh- cht cho

1.n.2 Cytochrom nh- cht cho1.n.3 Oxy nh- cht cho

(xy ho kh)


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1. Oxidoreductase

Lin quan ti cc phn ng xy ho kh mtrong nguyn t hydrogen hoc oxygenhoc cc in t -c chuyn i giacc phn t.

Lp c s l-ng nhiu gm c dehydrogenase

(hydride transfer), oxidase (in tchuyn n phn t oxygen), oxygenase(oxygen chuyn t phn t oxygen)vperoxidase (in t chuyn n

peroxide).V d: glucose oxidase (EC 1.1.3.4, tn h

thng, b-D-glucose:oxygen 1-oxidoreductase).


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ENZYME CLASSIFICATIONOxido-reductases: B sung xy hoc loi b nguyn thydro

1) B sung oxygen:a.Mono-oxygenase (b sung 1 nguyn t oxy)b.Di-oxygenase (b sung 2 nguyn t oxy)

2) Loi b hydro :Dehydrogenase (cn coenzyme mang hydro)

XH2 + AX + AH2 (coenzyme as FAD,NAD)-Oxidases: amino acid oxidase, catalase-Peroxidases:use H2O2 as electron acceptor


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2. Transferase

2.1 Chuyn mt nhm carbon

2.3 Acyltransferase

2.4 Glycosyltransferase

2.6.1 Transaminase

2.7 Chuyn nhm cha photpho

2.7.1 Nhm alcohol nh- cht nhn

(Vn chuyn nhm)


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2.TransferasesVn chuyn cc nhm chc nng:

1) Kinases: (chuyn phosphate t ATP n

phn t khc e.g.glucoseglucose-6-P

2) Transaminase: vn chuyn nhm amino.

3) Methyl transferase: vn chuyn nhmmethyl.


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3. Hydrolase 3.1 Esterase3..2 Glycosidase

3. 4 Peptidase

4. Lyase4.1 Carbon carbon lyase

4.1 Carbon Oxy lyase

4.1 Carbon Nitro lyase(Phn ng loi)

(Phn ng thu phn)


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3. HydrolasesB sung nc vo lin kt, thy phn n

-Esterase(choline esterase): phn hy linkt ester-Lipases: phn hy lin kt ester vo acidbo t do t triacylglycerols

-Peptidases: phn hy lin kt peptide -Nucleases: phn hy nucleic acids


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3. Hydrolase

Lin quan ti cc phn ng thu phn v s

nghch o ca chng. l mt lp ln cc enzymetrong lnh vc c ng ngh enzyme v bao gmesterase, glycosidase, lipase v protease.

V d: chymosin (EC 3.4.23.4, kh ng c tn hthng; cn gi l rennin).


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4. Lyase

Lin quan ti cc phn ng loi b trong nhm cc nguyn t b loi khi c cht. N baogm aldolase, decarboxylase, dehydratase vmt s pectinase nh-ng kh ng bao gmhydrolase.

V d: histidine ammonia-lyase (EC 4.3.1.3,Lhistidine ammonia-lyase; cn gi l histidase).


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4.Lyases1.B sung nc, ammonia, CO2, hoc loi b cc thnh

phn to ra lin kt iHO-CH- COOH Fumarase CH COOH

CH- COOH CH2 COOHMalic Fumaric

CarboxylasePyruvic Oxaloacetic

Pyruvate carboxylase

SynthetaseGlutamic Glutamine

Glutamine synthetase

2. Loi b 2 nhm ha hc ly nng lng t ATP


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5. Isomerase

5.1 Racemase v epimerase

5.3 Oxidorductase gia phnt

5.4 Transferase gia phn t

6.Ligase6.1 To lin kt carbon oxy

6.2 To lin kt carbon sulfur

6.1 To lin kt carbon - nitro

(Lin kt, sinh tng hp)


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5.IsomerasesThc hin nhiu qu trnh ng phn ha isomerization:1-Epimerase: ni chuyn ha mt ng tm lp th thnh cht

khc:UDP-glucose UDP-galactose

2-Mutase: chuyn nhm ha hc t v tr ny sang v tr khc: glucose-6-Pglucose-1-P-

3-Racemase: ni chuyn ha dng L thnh DL-alanineD-alanine

4-Aldose-ketose isomerase: ni chuyn ha aldoses &ketoses

glucose-6-Pfructose-6-P

5-Cis-trans isomerase: ni chuyn ha dng cis v trans

All cis retinol

All-

trans retinol


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5. Isomerase

Xc tc ng phn ho phn t v bao gmepimerase, racemase v intramoleculartransferase.

V d: xylose isomerase (EC 5.3.1.5, D-xyloseketolisomerase; thng gi l glucoseisomerase).


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1. Oxidoreductase... [dehydrogenase]

Xc tc cc phn ng xy ho kh, th-ng s dngcoenzyme nh- NAD+/FAD

Alcohol dehydrogenase [EC 1.1.1.1]ethanol + NAD+ -------> acetaldehyde + NADH

2. Transferase....

Xc tc chuyn i cc nhm chc nng Hexokinase [EC 2.7.1.2]

D-glu + ATP ----------> D-glu-6-P + ADP

Cc lp EC chnh


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3. Hydrolase .

Xc tc cc phn ng thu phn b sung n-c vocc lim kt cho C-C

Carboxypeptidase A [EC 3.4.17.1]

[aa-aa]n + H2O ----> [aa-aa] n-1 + aa

4. Lyase ....

B sung hoc loi b cc nhm vo lin kt C=C

Pyruvate decarboxylase [EC 4.1.1.1]pyruvate -----> acetaldehyde + CO2


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5. Isomerase [mutase]Xc tc ng phn ho (isomerization)

Maleate isomerase [EC 5.2.1.1]

maleate ----------> fumarate

6. Ligase

Kt hp 2 c cht c phn hu ATP

Pyruvate Carboxylase [EC 6.4.1.1]

PYR + CO2 + ATP ----> OAA + ADP + P


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6. Ligase

Cn -c bit n nh- synthetase, to ra mt

nhm t-ng i nh cc enzyme m c lin quan tivic hnh thnh lin kt covalent ni 2 phn t vinhau, i vi vic thu phn nucleosidetriphosphate.

V d: glutathione synthase (EC 6.3.2.3, g-Lglutamyl- L-cysteine:glycine ligase (ADP-forming);cn gi l glutathione synthetase).


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1st number: lp ca enzyme 2nd number: d-i lp bi kiu c cht hoclin kt b phn hu

3rd number: d-i lp bi s tip nhn in t

hoc kiu nhm b loi 4th number: s th t ca enzyme tm thy

Ch : S phn loi enzyme da trn phn ngho hc xc tc kh ng phi theo ngun gc (cc

chng hoc cc m ) ca enzyme trnh tAmino acid c th khc nhau

H thng s EC


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Hi ng enzyme quc t (InternationalEnzyme Commission)

IUBMB

H thng nh s: gm 4 s [1.2.3.4.] 1st # Major Class of Enzyme Activity

2nd # a subclass (type of bond acted upon)

3rd #... a subclass (group acted upon, cofactorrequired, etc...)

4th #... sth t th t m enzyme -c bsung vo danh sch.

S phn loi enzyme


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EC 1.2.3.1Tn th ng th-ng: aldehyde oxidase

Phn ng:

aldehyde + H2O + O2 = a carboxylic acid + H2O2

Tn khc: quinoline oxidase

Tn phn loi: aldehyde:oxygen oxidoreductase


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nh hng ca c cht ti tc ca phn ng

1-Nng c cht:

Tc ca phn ng ph thuc vo nng c cht.

nng c cht thp, tc ca phn ng tng t lthun vi nng c cht.

nng c cht cao, th tc tng tng chm hoc khngtng.


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Km

Km = affinity of substrate for enzyme; defined as[substrate] that elicits half-maximal reaction velocity


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Substrate concentration

Factors Influencing Enzyme ctivity

Figure 5.5c


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Nng enzyme

Phn ng xc tc t l vi nng enzyme


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Enzymes can be denatured by temperature and pH


Figure 5.6


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pH


Figure 5.5b


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0

0.2

0.4

0.6

0.8

1

1.2

0 2 4 6 8 10 12 14

pH

Relativeac

tivity(-)

C c enzyme phnngv i pH nh- thno

Complete stability

Reversible stability

Irreversible denaturation

C c enzyme kh c nhau c pH/activity profileskh cnhau


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pH

1- nh hng ca pH nn qu trnh ion ha trung tm xc tc:Nng H+ nh hng n tc phn ng theo mt s cch.

Qu trnh xc tc thng i hi enzyme v c cht c cc

nhm ha hc c trng trng thi ion ha hoc khng mtng tc.

VD: tnh xc tc cn nhm amino ca enzyme dng proton (-NH3+). pH kim nhm ny b kh proton v tc phn

ng chm li.


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nh hng ca pH nn s bin tnh caenzyme

pH qu cao hoc qu thp c th dn ti sbin tnh ca enzyme, bi v cu trc catrung tm xc tc ca phn t protein phthuc vo tnh cht ion ca cc amino acidchui cnh


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pH

Rel

tiveen

z

e

tivit

[-]

The ependence f enz ecatal edreacti ns isshown, a aseproducingenz e (a)andanacidproducingenz e ( ). ThepHsetpointcan echosen

changingrelati eamountsof othenz mes.

ver ingpH inactivati n


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DynamicpH

equili rium Cholinesterase

Produces utyricacid

pHoptimumat ~8.

reaseUrease

Produces H4+

and H-

pHoptimum elow 0

0.5

1

1.5

2

2.5

5 6 7 8 9 10

pH

Enzymeactivity

relative]

pH equili ium

UreaseUrease ChE

Catalytic uffers indetectionofnerveagents

Butyryl choline + H2O Butyricacid+Choline

Choline

Esterase

Response


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Response

10

8

4

2

pH

Time

Butyryl choline + H2O Butyricacid+Choline

CholineEsterase

ureaseUR A+ H2O 2NH+4 +CO2

SAFE

N SAFE

pH indicator reportscolourchange: lowpHgreen, highpH red.


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pH ti u ca enzyme khc nhau

pH ny th hot tnh ca enzyme t c ti mc ti

a.

For example, pepsin, a digestive enzyme in thestomach, is maximally active at pH 2, whereasother enzymes, designed to work at neutral pH, are

denatured by such an acidic environment


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fl i i i


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Temperature

Factors Influencing Enzyme Activity

Figure 5.5a


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Temperature

Tng s xc tc khi nhit tng

Gim s xc tc khi nhit gim


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S c ch hot tnh ca enzyme

a s thuc cha bnh da trn c ch c ch enzyme:

1-Methotrexate trong iu tr ung th c c ch chn lcnn qu trnh tng hp DNA ca t bo c tnh.

2-Aspirin c ch s tng hp prostaglandins ca qu trnhau m v au khp


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3- Thuc Sulfa c ch s tng hp folic acid cn thit choqu trnh trao i cht v gy bnh ca vi khun.

Nhiu cht c nh cyanide, carbon monoxide vpolychlorinated biphenols (PCBs) to ra nh hng tis sng thng qua s c ch enzyme.


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A) Cc cht c ch khng phc hi c:

Gy ra s c ch s bin i ha tr ca cu trcenzyme. e.g Cyanide l cht c ch khng phc hic; do lin kt ha tr vi mitochondrialcytochrome oxidase, n c ch tt c cc phn nglin quan ti vn chuyn in t.

Cc cht c ch khng phc hi c thng c chol cc cht c rt kh cu cha.


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B- Cc cht c ch phc hi c

1- Cc cht c ch cnh tranh

2- Cc cht c ch khng cnh tranh3- Cc cht c ch phi cnh tranh

F t I fl i E A ti it


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Competitive inhibition


Figure 5.7a, b



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Noncompetitive inhibition


Figure 5.7a, c


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1- Cc cht c ch cnh tranh

Cht c ch cnh tranh vi trung tm xc tc caenzyme.-Vmax: khng thay i-Km: tng ln

2- Cc cht c ch khng cnh tranh

Lin kt vi E hoc phc ES khng trung

tm xc tc ca enzyme.-Km: khng i-Vmax: gim


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3- Cc cht c ch phi cnh tranh

Lin kt vi phc ES.-Km: gim-Vmax: gim


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IU HA HOT NG CA ENZYME

Tc ca a s enzyme thay i theo nng c cht biv nng c cht trong t bo trong di ca Km. V thkhi nng c cht tng n c xu th a nng c chtv bnh thng.

Mt s enzyme c chc nng iu ha c trng p nghiu ng allosteric hoc thay i ha tr, hoc thay i tc tng hp ca enzyme khi cc iu kin sin l thay i.


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A. V tr lin kt Allosteric

- Cc enzyme Allosteric c iu ha bi cc phn tgi l cc yu t nh hng (effectors) lin kt khngha tr vi v tr ngoi trung tm xc tc.

- S hin din ca allosteric effector c th nh hng ti

i lc ca enzyme vi c cht hoc thay i ha tnhxc tc ti a ca enzyme hoc c hai.

- Cc cht nh hng (Effectors) c ch hot tnh caenzyme gi l cc yu t nh hng xu (negative

effectors). Cc yu t lm tng hot tnh ca enzymegi l yu t nh hng tt (positive effectors).

- Cc enzyme Allosteric thng c nhiu subunits vthng xc tc bc u ca chu trnh.


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B. iu ha enzyme thong qua s thay i lin kt ha tr

1. Phosphorylation v dephosphorylation:Phn ng Phosphorylation c xc tc bi h enzyme,gi l protein kinases, s dng adenosine triphosphatenh l cht cho phosphate.Gc Phosphate c phn hy t enzyme phospho

ha nh hot ng ca phosphoprotein phosphatase.

2. Phn hi ca enzyme vi qu trnh phospho ha: phthuc vo enzyme c trng, dng phospho ha c thhot ng nhiu hoc t hn enzyme khng phospho ha.

VD, qu trnh phospho ha ca glycogen phosphorylase(enzyme phn hy glycogen) tng hot tnh, m n bsung phosphate vo glycogen synthase (enzyme tng hpglycogen) gim hot tnh.


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C. Kch thch v km hm sinh tng hp enzyme

Cc enzyme cn iu ha qu trnh tng hp thng cnthit cho ch mt cng on ca s pht trin hoc dicc iu kin sinh l chn lc.

VD, tng mc insulin do lng glucose trong mu cao gyra tng sinh tng hp nhng enzyme chnh lin quan ting ha glucose. Ngc li, cc enzyme s dng khngi thng khng c iu ha bi s s thay i tc

sinh tng hp enzyme.

fl i i i


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Feedbackinhibition


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