Cold destabilisation of enzymes.

Area of Science:

• Biochemistry
• Physical Chemistry
• Protein Science

Background:

• Proteins exhibit complex thermal stability profiles.
• Cold instability is a poorly understood phenomenon in protein thermodynamics.
• Chymotrypsinogen serves as a model system for studying protein behavior.

Purpose of the Study:

• To investigate the thermal stability profile of chymotrypsinogen.
• To characterize the phenomenon of cold instability in proteins.
• To construct a reliable thermodynamic stability profile for chymotrypsinogen.

Main Methods:

• Differential scanning calorimetry (DSC) to measure heat capacities.
• Spectrophotometry at ordinary temperatures.
• Analysis of native and denatured protein states in undercooled solutions.

Main Results:

• Partial heat capacities of both native and denatured chymotrypsinogen decrease with temperature.
• A positive heat capacity difference (delta C) was observed in the accessible temperature range.
• delta C is predicted to change sign at temperatures below experimental reach.

Conclusions:

• The study provides a more reliable thermodynamic stability profile for chymotrypsinogen.
• Findings highlight differences compared to other proteins studied only near denaturation temperatures.
• Results align with theoretical predictions and low-temperature studies on lactate dehydrogenase.