The relationship between the structure and function of proteins is a foundational concept in biology. Enzyme denaturation exercises are a common way to illustrate this concept in introductory-level cell and molecular biology labs. Previously, our students manipulated reaction pH or temperature and quantified the effect of changing conditions on the rate of enzyme activity by measuring production of a colorimetric product in a spectrophotometer. Students watched enzyme rates approach zero as denaturing conditions were imposed. However, first-year students often struggle to link the observed loss in enzyme activity with protein structure changes in their reports. We therefore questioned whether this concept might be reinforced by asking students to take a step further and renature the enzyme by returning to optimal conditions after denaturation. In our updated lab procedure, adapted from Pitkin (1992), students measure turnip peroxidase activity in reactions with increasing pH, finally arriving at pH 9, where activity is minimal. Students then add different volumes of acid to the reactions and observe whether they have (1) decreased pH and (2) recovered enzyme activity. This approach reinforces the connection between reaction conditions and enzyme activity while providing additional data that can be used to discuss the relationship between enzyme structure and function. We present our procedure as a resource for other educators to implement in their own laboratory courses.
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