SAMENVATTING BIOCHEMIE
GIJSBERS
Inhoud
H5: Enzymes: concepts and kinetics............................................................3
WAT ZIJN ENZYMEN...................................................................................3
THERMODYNAMICA/ VRIJE ENERGIE..........................................................4
ENZYMEN...................................................................................................5
Enzymen helpen bij omzetting E vn ene nr andere vorm.......................6
Enzymen zijn altijd specifiek...................................................................6
Wrdr specificiteit?...................................................................................7
Classificatie.............................................................................................7
Enzymatische reacties en vrije energie..................................................7
Veranderen de snelheid, niet het evenwicht!!........................................9
Versnellen reactie dr faciliteren vn transitietoestand.............................9
DE ENZYMATISCHE REACTIE....................................................................10
Vorming van enzyme-substraat complex.............................................10
Actieve site...........................................................................................10
DE ACTIEVE SITE......................................................................................10
Algemene eigenschappen.....................................................................11
Bindingsenergie....................................................................................11
ENZYME KINETICA: MICHAELIS-MENTEN..................................................11
Reactiesnelheden.................................................................................11
Michaelis-Menten model.......................................................................13
Betekenis KM........................................................................................16
Betekenis Vmax....................................................................................16
Toepassingen: overgevoeligheid vr alcohol..........................................17
Methoden om KM en Vmax te bepalen.................................................18
Kinetica onder fysiologische condities (in het lichaam)........................18
ENZYM KINETICA.....................................................................................20
Biochemische reacties in de praktijk....................................................20
INHIBITIE VAN ENZYMATISCHE ACTIVITEIT..............................................22
1 AdamAdams123
, Inhibitoren............................................................................................22
Reversibele inhibitoren.........................................................................22
Reversibel inhibitoren: kinetische verschillen.......................................23
Irreversibele inhibitoren: active site mapping......................................27
Toepassing: werking van penincilline...................................................27
Eneklvoudige enzymen.........................................................................28
HOOFDSUTK 6: CATLYTIC STRATEGIES: CASE STUDIES.............................28
Enzymen: katalytische strategieeën.......................................................28
Enzymen...............................................................................................28
Case studies..........................................................................................29
Proteasen: chymotrypsine.......................................................................29
Proteolyse.............................................................................................29
Chymotrypsine: covalente katalyse......................................................30
Chymotrypsine: katalytische site..........................................................31
Chymotrypsine: peptide hydrolyse.......................................................32
Chymotrypsine: substraatvoorkeur.......................................................32
Chymotrypsine homologen (serine proteasen).....................................33
Subtilisine familie (serine proteasen)...................................................33
Serine proteasen...................................................................................34
Andere proteasen.................................................................................34
Protease inhibitoren..............................................................................35
Carbonic anhydrases...............................................................................35
Boosten van een snelle reactie.............................................................36
model met synthetisch analoog............................................................37
Proton shuttling en buffer.....................................................................37
RESTRICTIE-ENZYMEN.............................................................................37
specifieke DNA-knipping.......................................................................38
hydrolyse van fosfo-diesterbinding.......................................................38
Specificiteit...........................................................................................40
Vrije energie in een enzymatische reactie............................................40
Wrm knippen Re niet host-DNa.............................................................41
Geconserveerde katalytische kern.......................................................41
Myosines..................................................................................................41
2 AdamAdams123
, Mysosine ATPase act.............................................................................41
MYosine ATPase domein.......................................................................42
Conformatie-verandering......................................................................42
Veranderde conformatie houdt aan......................................................43
Enzymes met P-loop struct...................................................................44
CHAPTER 7: REGULATORY STRATEGIES.....................................................44
Regulatie vn enzymatische act...............................................................44
1. Allosterische controle.......................................................................44
2. Iso-enzymes......................................................................................45
3. Omkeerbare covalente modificatie...................................................45
4. Proteolytische activatie....................................................................45
5. controle vn transcriptie.....................................................................45
Allosterische controle..............................................................................45
Aspartaat transcarbamoylase (ATCase)................................................45
Iso-vormen, iso-zymen............................................................................49
lactaat dehydrogenase (LDH)...............................................................49
Covalente modificatie..............................................................................50
fosforylatie: gekatalyseerd via kinasen................................................50
De-fosforylatie: fosfatasen....................................................................51
bijv. proteïne kinase A (PKA).................................................................51
PKA activatie...........................................................................................52
Wrm fosforyleert PKA alleen een specifieke sequentie??.....................52
proteolytische activatie...........................................................................53
enzymes vs. pro-enzymen....................................................................53
Verteringsenzymen...............................................................................54
controle vn protease act.......................................................................55
Bloedstolling.........................................................................................55
H5: ENZYMES: CONCEPTS AND KINETICS
WAT ZIJN ENZYMEN
Enzyme = biologische katalysatoren = versnellen chemische reacties
zonder evenwicht te verleggen.
3 AdamAdams123
, Bepaald door thermodynamische wetten
THERMODYNAMICA/ VRIJE ENERGIE
2 thermodynamische wetten
1. Eerste hoofdwet: behoud van energie
Tot E + E omgeving = constant
E kan niet gemaakt of vernietigd worden enkel veranderen van
vorm: potentiële en kinetische E
2. Tweede hoofdwet: wet van toenemende wanorde
Totale entropie S neemt altijd toe
Biologische reacties: vormen gestructureerde moleculen
Lokaal minder entropie maar drdr meer entropie in de omgeving
Bijv door vrijzetten vn warmte: enthalpie H = hitte-inhoud
Entropieverandering ∆S
∆S omgeving ifv
1. Warmte vrijgezet door het systeem = -∆H systeem
2. Temp vn de omgeving T
−∆ Hsys
∆S omgeving =
T
Tot entropieverandering = ∆S = ∆S sys + ∆S omg
∆G = Gibbs Vrije E = maat vr entropie van sys en omg
Spontante reactie = totale entropie neemt toe
4 AdamAdams123
GIJSBERS
Inhoud
H5: Enzymes: concepts and kinetics............................................................3
WAT ZIJN ENZYMEN...................................................................................3
THERMODYNAMICA/ VRIJE ENERGIE..........................................................4
ENZYMEN...................................................................................................5
Enzymen helpen bij omzetting E vn ene nr andere vorm.......................6
Enzymen zijn altijd specifiek...................................................................6
Wrdr specificiteit?...................................................................................7
Classificatie.............................................................................................7
Enzymatische reacties en vrije energie..................................................7
Veranderen de snelheid, niet het evenwicht!!........................................9
Versnellen reactie dr faciliteren vn transitietoestand.............................9
DE ENZYMATISCHE REACTIE....................................................................10
Vorming van enzyme-substraat complex.............................................10
Actieve site...........................................................................................10
DE ACTIEVE SITE......................................................................................10
Algemene eigenschappen.....................................................................11
Bindingsenergie....................................................................................11
ENZYME KINETICA: MICHAELIS-MENTEN..................................................11
Reactiesnelheden.................................................................................11
Michaelis-Menten model.......................................................................13
Betekenis KM........................................................................................16
Betekenis Vmax....................................................................................16
Toepassingen: overgevoeligheid vr alcohol..........................................17
Methoden om KM en Vmax te bepalen.................................................18
Kinetica onder fysiologische condities (in het lichaam)........................18
ENZYM KINETICA.....................................................................................20
Biochemische reacties in de praktijk....................................................20
INHIBITIE VAN ENZYMATISCHE ACTIVITEIT..............................................22
1 AdamAdams123
, Inhibitoren............................................................................................22
Reversibele inhibitoren.........................................................................22
Reversibel inhibitoren: kinetische verschillen.......................................23
Irreversibele inhibitoren: active site mapping......................................27
Toepassing: werking van penincilline...................................................27
Eneklvoudige enzymen.........................................................................28
HOOFDSUTK 6: CATLYTIC STRATEGIES: CASE STUDIES.............................28
Enzymen: katalytische strategieeën.......................................................28
Enzymen...............................................................................................28
Case studies..........................................................................................29
Proteasen: chymotrypsine.......................................................................29
Proteolyse.............................................................................................29
Chymotrypsine: covalente katalyse......................................................30
Chymotrypsine: katalytische site..........................................................31
Chymotrypsine: peptide hydrolyse.......................................................32
Chymotrypsine: substraatvoorkeur.......................................................32
Chymotrypsine homologen (serine proteasen).....................................33
Subtilisine familie (serine proteasen)...................................................33
Serine proteasen...................................................................................34
Andere proteasen.................................................................................34
Protease inhibitoren..............................................................................35
Carbonic anhydrases...............................................................................35
Boosten van een snelle reactie.............................................................36
model met synthetisch analoog............................................................37
Proton shuttling en buffer.....................................................................37
RESTRICTIE-ENZYMEN.............................................................................37
specifieke DNA-knipping.......................................................................38
hydrolyse van fosfo-diesterbinding.......................................................38
Specificiteit...........................................................................................40
Vrije energie in een enzymatische reactie............................................40
Wrm knippen Re niet host-DNa.............................................................41
Geconserveerde katalytische kern.......................................................41
Myosines..................................................................................................41
2 AdamAdams123
, Mysosine ATPase act.............................................................................41
MYosine ATPase domein.......................................................................42
Conformatie-verandering......................................................................42
Veranderde conformatie houdt aan......................................................43
Enzymes met P-loop struct...................................................................44
CHAPTER 7: REGULATORY STRATEGIES.....................................................44
Regulatie vn enzymatische act...............................................................44
1. Allosterische controle.......................................................................44
2. Iso-enzymes......................................................................................45
3. Omkeerbare covalente modificatie...................................................45
4. Proteolytische activatie....................................................................45
5. controle vn transcriptie.....................................................................45
Allosterische controle..............................................................................45
Aspartaat transcarbamoylase (ATCase)................................................45
Iso-vormen, iso-zymen............................................................................49
lactaat dehydrogenase (LDH)...............................................................49
Covalente modificatie..............................................................................50
fosforylatie: gekatalyseerd via kinasen................................................50
De-fosforylatie: fosfatasen....................................................................51
bijv. proteïne kinase A (PKA).................................................................51
PKA activatie...........................................................................................52
Wrm fosforyleert PKA alleen een specifieke sequentie??.....................52
proteolytische activatie...........................................................................53
enzymes vs. pro-enzymen....................................................................53
Verteringsenzymen...............................................................................54
controle vn protease act.......................................................................55
Bloedstolling.........................................................................................55
H5: ENZYMES: CONCEPTS AND KINETICS
WAT ZIJN ENZYMEN
Enzyme = biologische katalysatoren = versnellen chemische reacties
zonder evenwicht te verleggen.
3 AdamAdams123
, Bepaald door thermodynamische wetten
THERMODYNAMICA/ VRIJE ENERGIE
2 thermodynamische wetten
1. Eerste hoofdwet: behoud van energie
Tot E + E omgeving = constant
E kan niet gemaakt of vernietigd worden enkel veranderen van
vorm: potentiële en kinetische E
2. Tweede hoofdwet: wet van toenemende wanorde
Totale entropie S neemt altijd toe
Biologische reacties: vormen gestructureerde moleculen
Lokaal minder entropie maar drdr meer entropie in de omgeving
Bijv door vrijzetten vn warmte: enthalpie H = hitte-inhoud
Entropieverandering ∆S
∆S omgeving ifv
1. Warmte vrijgezet door het systeem = -∆H systeem
2. Temp vn de omgeving T
−∆ Hsys
∆S omgeving =
T
Tot entropieverandering = ∆S = ∆S sys + ∆S omg
∆G = Gibbs Vrije E = maat vr entropie van sys en omg
Spontante reactie = totale entropie neemt toe
4 AdamAdams123
