第 5 章 酶与辅酶 (enzymes and coenzymes)
DESCRIPTION
第 5 章 酶与辅酶 (enzymes and coenzymes). 主要内容:主要讲解酶的化学本质、结构和特性;酶促反应动力学;酶的作用机理;酶活性的调节;酶的应用;还介绍了别构酶、共价调节酶、同工酶等的概念、性质、生物学意义。. 第 1 节 维生素与辅酶. 主要内容 :. 主要介绍各种维生素的结构、性质和功能,维生素与辅酶的关系。. 一、维生素的概念和类别. (一)维生素的概念. (二)分类. 脂溶性维生素: A 、 D 、 E 、 K. 维生素. 水溶性维生素: B 族( B 1 、 B 2 、 B 3 、 B 5 、 - PowerPoint PPT PresentationTRANSCRIPT
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5 (enzymes and coenzymes)
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1
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ADEK BB1B2B3B5 B6B7B11B12 C
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A 1
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A-
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2 3 1 2
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+ VitA OH CHO
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11- 11-cis-Retinal
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11-schiff base Schiff
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D 1 DD D
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25- 1,25- D3
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2 1 D
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2 3
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E 1 6-
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2 E
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3 1 2 3
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K KK1K2K3K4 K1K2 K3K4
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1
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2 KVit K
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vitK 7910vitK
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B 1B1thiamine 1
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+ATP TPP+AMP
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2 B1TPP- -
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2B2riboflavin 1
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2 B2FMNFADFMNFAD
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3 FMNFAD FMNFAD 260nm375nm450nm260nm375nm450nm
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3B3pantothenic acid 1
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2 B3CoACoA
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4B5pp nicotinamide 1 B5 -3- nicotinic acid -3- nicotinamide
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2 B5NADNADPNADNADP
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OxRed
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OxRedNAD+ NADH + H+(NAD) (NADH2)NADP+ NADPH + H+(NADP) (NADPH2)
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5B6 1
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( PLP )( PMP )
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2 PLPPMP
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6B7biotin 1
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2 B7CO2
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7B11folic acid, FA; pteroyl glutamic acid 1
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2 5678Tetrahydrofolate, THFA, THF
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8B12cyanocobalamin 1 B12
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cyanocobalamin
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2 5
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B12
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B12B12
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B
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C ascorbic acid 1 Ascorbic acid ( vitamin C )
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2
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3 1 2C C 3 4 5
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CoQ()n=6~10n=6n=10::
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Lipoic Acid6,8-
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: -SH
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2(Enzyme)
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enzymes(Cofactor)(Cofactor)CofactorsFe2+, Mn2+(metalloorganic), (Coenzymes)(prosthetic group):
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(Holoenzyme): ()(specified functional groups)(carriers)
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1 1 2 3
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2H2O22H2O+O2
75.24kJ/mol48.9kJ/molH2O28.36kJ/mol
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2 1 (molecular ratio) 10710131081020 2H2O22H2O+O2 1mol H2O2 5106mol H2O21mol Fe3+610-4molH2O2
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(turnover number,)1000-12500 -1100 00036000000 ?
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234 5
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1Most enzymes are proteins 1926Sumner 1930Northrop
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2080RNADNA 2RNA 1982T. CechrRNARNA Thomas Cech, University of Colorado at Boulder, USA
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1983S.AltmanRNaseP20%80%RNARNasePRNAE. coli tRNA Sidney Altman Yale University New Haven, CT, USA
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CechAltmanRNAribozyme21989 3abzyme N 1986SchultzLernerScience
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4DNA 1995CuenoudDNA
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1 2=+coenzymeprosthetic groupmonomeric enzymeoligomeric enzyme multienzyme complex
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1961enzyme commission 1 :G-6-PF-6-P G-6-P
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2:1 +- + :-2 +H2O +
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2recommended name1 2 341: 6
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2: 4ECEnzyme CommissionEC ...EC 1.1.1.1Enzyme Handbook Thomas E BarmanVol I, Vol II 1969 Enzyme HandbookThomas E. Barman Supplement I, 1974
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123456 :104 23EDTA- 4
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(U/ml)(ml)
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enzyme activity, 11initial velocity or initial speed2 3pH4[S]>>[E]
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2 1enzyme activity2specific activity mgU/mg = U/ml/mg/ml3TN or kcat)4molecular activity 5catalytic center activity
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3. 1spectrophotometry 10-9mol/L
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2fluorometry 10-12mol/LTyrTrpPheNADHNADPHFMNFAD 3(enzyme coupling assay) 4electrochemical method
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kinetics 1 : ESE+P V[ES]
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1913MichaelisMenten
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2 : 3: 2 [S]>>[E][S] [ES][S] V[ES]
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43
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3 1 2Vmax 3 4 5
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4 1Km 2KmKm 3KmpH KmpH 4KmKsKmKs
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5 1v[S] 2Lineweaver-Burk
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3v Eadie-Hofstee
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4 [S]/v [S]Hanes-Woolf
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5 EisenthalCornish-Bowden
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: sequential reactions ping pong reactions orderd reactions random reactions
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1ordered reactions ordered Bi Bi
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2random reactions Random Bi Bi
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3ping pong reactionsuni uni uni uni ping pong or Ping Pong Bi Bi
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1 [S]>>[E]V[E] 2V[E] pH 1pHoptimum pH 2pH ( 1 ) pHES ( 2 ) pH
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1optimum temperature pH, , pH, :
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1irreversible inhibition 2(reversible inhibition) 1competitive inhibition
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2noncompetitive inhibition
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3uncompetitive inhibition
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specificity 1absolute specificity
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2relative specificity 1group specificity 2 A B
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3stereospecificity 1D-L- 2 3
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1lock and Key theory 1894 Fischer
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2
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3induced-fit theory 1958 Koshland
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active center 1 GluASP-COOHLys-NH2HisSer-OHCys-SHTyr
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1 proximity and orientation effect :
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2strain and distortion
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3acid-base catalysis
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4covalent catalysis 5
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1Lysozyme
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2chymotrypsin
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3Acarboxypeptidase ACpA
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:
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:
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allosteric enzyme allosteric effect 1 2
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1positive cooperative effect
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2negative cooperative effect 3
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4
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koshlandsaturation ratio, Rs RS=81 RS81
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1symmetry or concerted model,MWC 1965MonodWymanChangeux :
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2sequential modelKNF 1966KoshlandNemethyFilmer :
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covalently modulated enzymes /////S-S/SH6
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1. G-1-P
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2
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isoenzyme or isozyme
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lactate dehydrogenase, LDH 1
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2
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1pepsinogen 2trypsinogen
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3chymotrypsinogen
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immobilized enzyme