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Alcohol metabolism – the role of K M

Alcohol metabolism – the role of K M. TACHYCARDIA. Mitochondrial Acetalde hyde redu ctase K M value - low. Cytosolic Acetaldeh y d e dehydrogenase K M value - high. Enzymes - K M values. K M. K M ~ Dissociation constant for ES , if k 2 >> k 3

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Alcohol metabolism – the role of K M

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  1. Alcohol metabolism – the role of KM TACHYCARDIA Mitochondrial Acetaldehyde reductase KMvalue - low Cytosolic Acetaldehyde dehydrogenase KMvalue - high

  2. Enzymes - KMvalues

  3. KM KM~ Dissociation constantfor ES, if k2 >> k3 KMvalue is high: ES formation is weak KMvalue is low: assotiation

  4. Importance of the Vmaxvalue Turnover number:

  5. Inhibition of Enzymes • Irreversible • Ser-OH • Cys-SH • Reversible Enzyme Enzyme + HF Diisopropylfluorophosphate

  6. Inhibitions of enzymes • -SH enzymes + HI Enzyme Enzyme monoiodacetamide

  7. Competitive inhibition of succinate-dehydrogenase by malonate

  8. Competitive inhibition + S + I Ki = dissociation constant for complex

  9. Competitive inhibition of succinate-dehydrogenase by malonate No inhibitor [Enzyme] Substrate + competitive inhibitor [Inhibitor 1] [Inhibitor 2]

  10. Competitive inhibition +P + S + I Ki = Dissociation constans of complex

  11. Competitive inhibition of succinate-dehydrogenase by malonate V [mM/min] Vmax Enzyme without ihhibitor Enzyme + inhibitor (1) Vmax/2 Enzyme + inhibitor (2) Substrate [M]

  12. Competitive inhibition E + inhibitor-2 E + inhibitor-1 1/v Enzyme alone 1/VMAX 1/[S] y=a*x+b

  13. Competitive inhibition – Lineweawer-Burk plots Enzyme + Inhibitor 2 Enzyme + Inhibitor 1 Enzyme

  14. Competitive inhibition • KMvalue - increase, Vmax- constant • KI =/= KS • Inhibition depends on [S]/[I].

  15. Competitive inhibition E + inhibitor2 E + inhibitor1 1/v Enzyme only 1/VMAX 1/[S] y=a*x+b

  16. Ethanol N Methanol N Ethyleneglycol

  17. Competitive inhibition

  18. Noncompetitive inhibition + S + I + P + S

  19. Noncompetitive inhibition • KMvalue is constant • VMax- decrease • Inhibitor-binding – different of substate binding site • EIS complex – is inactive

  20. Nonkompetitive inhibition I2 1/v I1 Kontroll 1/Vmax -1/KM 1/[S]

  21. Noncompetitive inhibition Metal / Enzyme + CN-, EDTA Partially noncompetitive inhibitor

  22. Uncompetitive inhibition Both KM& Vmax values - decrease 1/v I1 Enzyme alone 1/[S]

  23. Inhibition of mixed type KM- increase Vmax decrease 1/v I1 Control 1/[S]

  24. Turnover number • Number of molecules converted by 1 molecule of enzyme • Vmax = k3*[Et] • k3[sec-1] • i.e.: 10-6 M carbonic anhydrase • 0.6 M of H2CO3in 1 secundum

  25. Turnover number

  26. Activity units • Enzyme activity units: • 1 E (U): 1 mmole/min 25 oC • 1 Catal (SI): 1 mole/sec • Specific activity: • mmo/min/mg protein • mol/sec/mg protein

  27. Enzyme activities – in everyday medical practice

  28. Enzyme activities – in everyday medical practice

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