• 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)

Problems 7a-d,8a,b

Regulation

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

Competitive inhibition

Noncompetitive inhibition

Regulation

Reversible– Substrate level regulation – Competitive inhibitors– Noncompetitive inhibitors– Allosteric regulation (activators and

inhibitors) – Covalent modification (reversible)– Proteolytic cleavage

Reversible covalent modification

Phosphorylation

Dephosphorylation

Proteolytic cleavage

Only extracellular

Metabolism

Energy flow in cells