Enzyme Regulation MUDR. MARTIN VEJRAŽKA, PHD.

Transcription

1 Enzyme Regulation MUDR. MARTIN VEJRAŽKA, PHD.

2 Enzyme regulation Body IS NOT in chemical equilibrium Equilibrium = death Life: Homeostasis, steady-state

3 Catalysisin a closedsystem Without catalyst Equilibrium is set up slowly

4 Catalysisin a closedsystem With a catalyst The same equilibrium as w/o catalyst but much faster

5 Openedsystem Constant values but not equilibrium steady-state homeostasis Regulation changes values (not only time to reach them)

6 Enzyme regulation Controls concentrations Corresponds to needs delivery

7 Enzyme regulation Disrupted regulation causes disease Kinases and phosphatases: cancer Excess of some substance (cholesterol atherosclerosis, uric acid gout )

8 Laboratorydiagnostics or of concentration of some substance / formation / elimination or Measuring activity of an enzyme

9 acetylosalicylic acid Drugs Many drugs change activity of some enzyme (mostly inhibitors) simvastatine allopurinol omeprazole sildenafil vincristine tetracycline sulbactam atorvastatine enalaprile co-trimoxazole

10 Enzymesand drugs Effect of many drugs is changed by action of enzymes cytochrome P 450 conjugation acetylation

11 Enzyme regulation Gene expression Conversion of proenzyme Catalitic activity Enzyme degradation Pro-enzyme ENZYM substrate product Substrate delivery Availability of co-enzymes Product take-away

12 Concentrationof enzyme

13 Inductionand repression Gene expression Conversion of proenzyme Catalitic activity Enzyme degradation Pro-enzyme ENZYM substrate product Substrate delivery Availability of co-enzymes Product take-away

14 Induction Inducible enzyme Constitutive enzyme induction bazální Basal activity aktivita

15 Induction ethanol acetaldehyde acetate 1. Alcohol dehydrogenase and aldehyde dehydrogenase - constitutive enzymes 2. MEOS - inducibile

16 Repression Repression by product

17 Conversionofpro-enzyme Gene expression Conversion of proenzyme Catalitic activity Enzyme degradation Pro-enzyme ENZYM substrate product Substrate delivery Availability of co-enzymes Product take-away

18 Bloodclotting XII XIIa XI XIa IX IXa + VIIIa VIIa III VII X Xa + Va II IIa XIIIa I Ia Fibrine net

19 Degradationofenzyme Gene expression Conversion of proenzyme Catalitic activity Enzyme degradation Pro-enzyme ENZYM substrate product Substrate delivery Availability of co-enzymes Product take-away

20 Degradationofenzyme Often depends on conformation Enzyme with substrate bound to active site is protected

21 Degradationofenzyme Grapefruite juice increases degradation of intestinal cytochrome P450 Activity drops by one half within several hours Availability and effect of many drugs is increased

22 Substratedelivery

23 Concentrationofsubstances Gene expression Conversion of proenzyme Catalitic activity Enzyme degradation Pro-enzyme ENZYM substrate product Substrate delivery Availability of co-enzymes Product take-away

24 Compartments Cytosolic isoenzyme Mitochondrial isoenzyme

25 Compartments Macromolecular complexes of enzymes Passing substrates - products, high local concentrations Transfer of conformational changes

26 Substrateconcentration Substrate concentration Concentration of free substrate

27 Catalyticefficacy

28 Catalyticefficacy Gene expression Conversion of proenzyme Catalitic activity Enzyme degradation Pro-enzyme ENZYM substrate product Substrate delivery Availability of co-enzymes Product take-away

29 Catalyticefficacy Inhibitors drugs, poisons Allosteric modification Small molecules Covalent modifications Interactions between subunits

30 Inhibitors Competitive Compete with substrate Other Non-competitive, acompetitive, mixed

31 Competitiveinhibition Inhibitor often resembles substrate Effect depends on Concentration ratio Affinity ratio Reversible

32 Copetitiveinhibitors v Kontrola control Komp. inh. comp. inh. [S]

33 Competitiveinhibition N N H N N xantinoxidase HO N N H N N OH OH hypoxantine OH uric acid N H N N N OH allopurinol

34 Noncompetitiveinhibition Inhibitor does not compete with substrate Decreases amount of working enzyme Reversible or irreversible

35 Noncompetitiveinhibitors v Kontrola control Nekomp. inh. noncomp. inh. [S]

36 Noncompetitiveinhibitor Salicylic acid + Acetylsalicylic acid Ser Photos from Bayer Health Care: (11/2007)

37 Allosteric regulation

38 Allostericmodifiers Do not resemble substrates nor co-enzymes Bind to a site distant from active site Change conformation of enzyme

39 Allostericinhibitors enzyme Substrate Allosteric inhibitor

40 Allostericinhibitors enzyme Substrate Allosteric inhibitor

41 Allostericregulation macromolecule Feed-back inhibiton by the last low-molecular weight molecule

42 Allostericregulation macromolecule The first irreversible reaction is inhibited

43 Allostericregulation

44 Cooperativity v Kontrola control Aloster. inh. allost. inh. [S]

45 Cooperativityofsubstrates

46 Cooperativityofsubstrates

47 Cooperativityofsubstrates

48 Cooperativityofsubstrates

49 Cooperativity v Little substrate: Sparing A lot of substrate: Tidying up [S]

50 Covalentmodiffication Reversible phosphorylation of OH Beyond active site Kinases (phosphate from ATP) Ser, Thr Tyr Phosphatases (dephosphorylation hydrolysis of ester bond)

51 Phosphorylation Ser Thr Tyr ATP P i ATP P i ATP P i ADP H 2 O ADP H 2 O ADP H 2 O

52 Phosphorylation Neuronal and hormonal regulation ATP ATP ATP ATP

53 Assemblyofsubunits (protein-protein interactions) Catalytic subunit Regulatory subunit binding camp calmodulin binds Ca 2+ G-proteins bind GTP/GDP