Malonate against succinate.

Malonate looks like succinate and takes the active site of succinic dehydrogenase; raising substrate out-competes it so the same Vmax is reached.

With 10 mM malonate present, raise succinate until velocity is back to 90 % of Vmax.

A competitive inhibitor permanently lowers Vmax.

• Conditions that alter a protein's tertiary structure change enzyme activity: temperature, pH, substrate concentration, and the binding of specific chemicals that regulate it.
• Enzymes work within a narrow range of temperature and pH. Each shows its highest activity at an optimum temperature and an optimum pH, and activity falls on either side of the optimum.
• Low temperature keeps an enzyme temporarily inactive, while high temperature destroys its activity because heat denatures proteins.
• As substrate concentration rises, reaction velocity rises at first and then levels off at a maximum velocity (Vmax) that more substrate cannot exceed. There are fewer enzyme molecules than substrate molecules, and once all are occupied no free enzyme is left for the extra substrate.
• When a chemical that binds to the enzyme shuts off its activity, the process is inhibition and the chemical is an inhibitor.
• A competitive inhibitor closely resembles the substrate and competes with it for the substrate-binding site, so the substrate cannot bind and activity falls. Malonate inhibits succinic dehydrogenase because it closely resembles the substrate, succinate.
• Competitive inhibitors are often used to control bacterial pathogens.

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