5 (enzymes and coenzymes)

1

ADEK BB1B2B3B5 B6B7B11B12 C

A 1

A-

2 3 1 2

+ VitA OH CHO

11- 11-cis-Retinal

11-schiff base Schiff

D 1 DD D

25- 1,25- D3

2 1 D

2 3

E 1 6-

2 E

3 1 2 3

K KK1K2K3K4 K1K2 K3K4

1

2 KVit K

vitK 7910vitK

B 1B1thiamine 1

+ATP TPP+AMP

2 B1TPP- -

2B2riboflavin 1

2 B2FMNFADFMNFAD

3 FMNFAD FMNFAD 260nm375nm450nm260nm375nm450nm

3B3pantothenic acid 1

2 B3CoACoA

4B5pp nicotinamide 1 B5 -3- nicotinic acid -3- nicotinamide

2 B5NADNADPNADNADP

OxRed

OxRedNAD+ NADH + H+(NAD) (NADH2)NADP+ NADPH + H+(NADP) (NADPH2)

5B6 1

( PLP )( PMP )

2 PLPPMP

6B7biotin 1

2 B7CO2

7B11folic acid, FA; pteroyl glutamic acid 1

2 5678Tetrahydrofolate, THFA, THF

8B12cyanocobalamin 1 B12

cyanocobalamin

2 5

B12

B12B12

B

C ascorbic acid 1 Ascorbic acid ( vitamin C )

2

3 1 2C C 3 4 5

CoQ()n=6~10n=6n=10::

Lipoic Acid6,8-

: -SH

2(Enzyme)

enzymes(Cofactor)(Cofactor)CofactorsFe2+, Mn2+(metalloorganic), (Coenzymes)(prosthetic group):

(Holoenzyme): ()(specified functional groups)(carriers)

1 1 2 3

2H2O22H2O+O2

75.24kJ/mol48.9kJ/molH2O28.36kJ/mol

2 1 (molecular ratio) 10710131081020 2H2O22H2O+O2 1mol H2O2 5106mol H2O21mol Fe3+610-4molH2O2

(turnover number,)1000-12500 -1100 00036000000 ?

234 5

1Most enzymes are proteins 1926Sumner 1930Northrop

2080RNADNA 2RNA 1982T. CechrRNARNA Thomas Cech, University of Colorado at Boulder, USA

1983S.AltmanRNaseP20%80%RNARNasePRNAE. coli tRNA Sidney Altman Yale University New Haven, CT, USA

CechAltmanRNAribozyme21989 3abzyme N 1986SchultzLernerScience

4DNA 1995CuenoudDNA

1 2=+coenzymeprosthetic groupmonomeric enzymeoligomeric enzyme multienzyme complex

1961enzyme commission 1 :G-6-PF-6-P G-6-P

2:1 +- + :-2 +H2O +

2recommended name1 2 341: 6

2: 4ECEnzyme CommissionEC ...EC 1.1.1.1Enzyme Handbook Thomas E BarmanVol I, Vol II 1969 Enzyme HandbookThomas E. Barman Supplement I, 1974

123456 :104 23EDTA- 4

(U/ml)(ml)

enzyme activity, 11initial velocity or initial speed2 3pH4[S]>>[E]

2 1enzyme activity2specific activity mgU/mg = U/ml/mg/ml3TN or kcat)4molecular activity 5catalytic center activity

3. 1spectrophotometry 10-9mol/L

2fluorometry 10-12mol/LTyrTrpPheNADHNADPHFMNFAD 3(enzyme coupling assay) 4electrochemical method

kinetics 1 : ESE+P V[ES]

1913MichaelisMenten

2 : 3: 2 [S]>>[E][S] [ES][S] V[ES]

43

3 1 2Vmax 3 4 5

4 1Km 2KmKm 3KmpH KmpH 4KmKsKmKs

5 1v[S] 2Lineweaver-Burk

3v Eadie-Hofstee

4 [S]/v [S]Hanes-Woolf

5 EisenthalCornish-Bowden

: sequential reactions ping pong reactions orderd reactions random reactions

1ordered reactions ordered Bi Bi

2random reactions Random Bi Bi

3ping pong reactionsuni uni uni uni ping pong or Ping Pong Bi Bi

1 [S]>>[E]V[E] 2V[E] pH 1pHoptimum pH 2pH ( 1 ) pHES ( 2 ) pH

1optimum temperature pH, , pH, :

1irreversible inhibition 2(reversible inhibition) 1competitive inhibition

2noncompetitive inhibition

3uncompetitive inhibition

specificity 1absolute specificity

2relative specificity 1group specificity 2 A B

3stereospecificity 1D-L- 2 3

1lock and Key theory 1894 Fischer

2

3induced-fit theory 1958 Koshland

active center 1 GluASP-COOHLys-NH2HisSer-OHCys-SHTyr

1 proximity and orientation effect :

2strain and distortion

3acid-base catalysis

4covalent catalysis 5

1Lysozyme

2chymotrypsin

3Acarboxypeptidase ACpA

:

:

allosteric enzyme allosteric effect 1 2

1positive cooperative effect

2negative cooperative effect 3

4

koshlandsaturation ratio, Rs RS=81 RS81

Hill Hill : Hill nHillHill n=1 n>1 n

1symmetry or concerted model,MWC 1965MonodWymanChangeux :

2sequential modelKNF 1966KoshlandNemethyFilmer :

covalently modulated enzymes /////S-S/SH6

1. G-1-P

2

isoenzyme or isozyme

lactate dehydrogenase, LDH 1

2

1pepsinogen 2trypsinogen

3chymotrypsinogen

immobilized enzyme