1. Bioreactors Engineering
Enzymes
Class work 1

2. Bioreactors Engineering
Enzymes

3. Bioreactors Engineering
Enzymes

4. Bioreactors Engineering
Enzymes
Class work 2

5. Bioreactors Engineering
Enzymes
Home work 1

6. Bioreactors Engineering
Enzymes
End of Enzyme kinetics

7. Inhibited enzyme kinetics
Bioreactors Engineering
Enzymes
Inhibited enzyme kinetics
Certain compounds may bind to enzymes and reduce their activity. These compounds are known to be enzyme inhibitors.
Enzyme inhibitions may be irreversible or reversible.
Irreversible inhibitors such as heavy metals (lead, cadmium, and mercury ) form a stable complex with enzyme and reduce enzyme activity. Such enzyme inhibition may be reversed only by using chelating agents such as EDTA (ethylene-diamine-tetra-acetic acid) and citrate.
Reversible inhibitors may dissociate more easily from the enzyme after binding.
The three major classes of reversible enzyme inhibitions are
Competitive
Noncompetitive,
Uncompetitive inhibitions,
Uncompetitive substrate inhibitions
The substrate may
act as an inhibitor in
some cases.

8. Bioreactors Engineering
Enzymes
Inhibited enzyme kinetics
Competitive inhibitors
Competitive inhibitors are usually substrate analogs and compete with substrate for the active site of the enzyme. The Competitive enzyme scheme can be described as; ES
E + S K1
K-1
E + P KI K2 EI + I

9. Bioreactors Engineering
Enzymes
Inhibited enzyme kinetics
Competitive inhibitors

10. Bioreactors Engineering
Enzymes
Inhibited enzyme kinetics
Competitive inhibitors
The net effect of competitive inhibition is an increased value of Km, app, and therefore, reduced reaction rate. competitive inhibition can be overcome by high concentrations of substrate.
Fig. describes competitive enzyme inhibition in the form of a double-reciprocal plot.

11. Bioreactors Engineering
Enzymes
Inhibited enzyme kinetics
Noncompetitive inhibitors
Noncompetitive inhibitors are not substrate analogs. Inhibitors bind on sites other than the active site and reduce enzyme affinity to the substrate. Noncompetitive enzyme inhibition can be described as follows;

12. Bioreactors Engineering
Enzymes
Inhibited enzyme kinetics
Noncompetitive inhibitors

13. Bioreactors Engineering
Enzymes
Inhibited enzyme kinetics
Noncompetitive inhibitors
The net effect of noncompetitive inhibition is a reduction in High substrate concentrations would not overcome noncompetitive inhibition. Other reagents
need to be added to block binding of the inhibitor to the enzyme. In some forms
of noncompetitive inhibition is reduced and is increased. This occurs if the complex ESI can form product.

14. Bioreactors Engineering
Enzymes
Inhibited enzyme kinetics
Uncompetitive inhibitors
Uncompetitive inhibitors bind to the ES complex only and have no affinity for the enzyme itself. The scheme for uncompetitive inhibition is

15. Bioreactors Engineering
Enzymes
Inhibited enzyme kinetics
Uncompetitive inhibitors

16. Bioreactors Engineering
Enzymes
Inhibited enzyme kinetics
Uncompetitive inhibitors
The net effect of uncompetitive inhibition is a reduction in both Vm and Km values. Reduction in Vm has a more pronounced effect than the reduction in Km and the net result is a reduction in reaction rate. uncompetitive inhibition is described in Fig. in the form of a double-reciprocal plot.

17. Bioreactors Engineering
Enzymes
Inhibited enzyme kinetics
Uncompetitive substrate inhibitors
High substrate concentrations may cause inhibition in some enzymatic reactions,
known as substrate inhibition. Substrate inhibition is graphically described in Fig.
The reaction scheme for uncompetitive substrate inhibition is;
Fig. Comparison of substrate inhibited and uninhibited enzymatic reactions.

18. Bioreactors Engineering
Enzymes
Inhibited enzyme kinetics
Uncompetitive substrate inhibitors

19. Bioreactors Engineering
Enzymes

20. Bioreactors Engineering
Enzymes
Inhibited enzyme kinetics
Uncompetitive substrate inhibitors
A double-reciprocal plot describing substrate inhibition is give in the Fig. below;

21. Bioreactors Engineering
Enzymes

22. Bioreactors Engineering
Enzymes

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Enzymes

24. Bioreactors Engineering
Enzymes

25. Bioreactors Engineering
Enzymes
End of enzyme inhibition