By Tricia Lobo, Updated Aug 30, 2022
Enzymes accelerate chemical reactions by lowering activation energy. Most enzymes perform best between 35 °C and 40 °C, a range where increased kinetic energy enhances substrate binding without causing denaturation. Exceeding this window can irreversibly unfold the protein and halt activity.
Select a reliable method to quantify product formation at each temperature point. Common options include spectrophotometry—converting absorbance to concentration using a calibration curve—or fluorescence assays that correlate intensity with product amount.
Combine enzyme and substrate in a sealed scintillation vial to prevent evaporation. Place the vial in a larger beaker of water and mount the beaker on a heating plate. Insert a calibrated thermometer into the beaker to monitor the solution temperature accurately.
Begin by taking a 100‑µL aliquot at ambient temperature (~25 °C). Activate the heating plate and collect 100‑µL samples at incremental temperatures—30.5 °C, 31 °C, 31.5 °C, etc.—until reaching 40 °C. Ensure each sample is processed immediately to avoid temperature drift.
Determine product concentration for each aliquot using the chosen assay. Plot concentration (or reaction rate) versus temperature. The peak of this curve identifies the enzyme’s optimal temperature. Temperatures above 40 °C typically show a decline in activity, indicating onset of denaturation.
