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Enzymes, con't. Substrate Activation (catalytic mechanisms). Strain on substrate Weakens bonds Makes more accessible for reaction Acid/base catalysis Covalent (nucleophilic/electrophilic) catalysis. Enzyme kinetics. Study of reaction rates—can tell lots about reaction mechanisms.

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Substrate activation catalytic mechanisms
Substrate Activation(catalytic mechanisms)

  • Strain on substrate

    • Weakens bonds

    • Makes more accessible for reaction

  • Acid/base catalysis

  • Covalent (nucleophilic/electrophilic) catalysis


Enzyme kinetics

Enzyme kinetics

Study of reaction rates—can tell lots about reaction mechanisms


Michaelis menton kinetics saturation kinetics
Michaelis-Menton Kinetics(saturation kinetics)




Simplifying assumptions
Simplifying assumptions

  • No back reaction

  • k3 is rate limiting

  • [ES] is constant (steady state assumption)



  • Km

    • Measure of binding affinity (roughly)

    • The lower the Km, the tighter the binding

  • Vmax

    • Maximum rate of enzyme

    • Determined by turnover number (kcat)

How best to calculate them?


Double reciprocal plot lineweaver burk
Double-reciprocal plot(Lineweaver-Burk)




Regulation1
Regulation

  • Irreversible inhibitors—generally not natural part of cell

    • Drugs and toxins

    • Covalent modification

    • Aspirin

  • Reversible

    • Substrate level regulation

    • Competitive inhibitors

    • Noncompetitive inhibitors

    • Allosteric regulation (activators and inhibitors)

    • Covalent modification (reversible)

    • Proteolytic cleavage




Regulation2
Regulation

Reversible

  • Substrate level regulation

  • Competitive inhibitors

  • Noncompetitive inhibitors

  • Allosteric regulation (activators and inhibitors)

  • Covalent modification (reversible)

  • Proteolytic cleavage


Reversible covalent modification

Reversible covalent modification

Phosphorylation

Dephosphorylation


Proteolytic cleavage

Proteolytic cleavage

Only extracellular


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