Km Measure of binding affinity (roughly) The lower the Km, the tighter the binding Vmax
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• 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?
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Double-reciprocal plot(Lineweaver-Burk)
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Problems 7a-d,8a,b
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Regulation
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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
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Competitive inhibition
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Noncompetitive inhibition
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Regulation
Reversible– Substrate level regulation – Competitive inhibitors– Noncompetitive inhibitors– Allosteric regulation (activators and
inhibitors) – Covalent modification (reversible)– Proteolytic cleavage
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Reversible covalent modification
Phosphorylation
Dephosphorylation
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Proteolytic cleavage
Only extracellular
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Metabolism
Energy flow in cells