AP Syllabus focus:
‘In some cases, denatured enzymes can recover their structure, allowing catalytic activity to return.’
Enzymes depend on precise 3D folding for catalysis, but some structural disruptions are not permanent. This page explains when denaturation can be reversible, how recovery occurs, and why recovery sometimes fails.
What “reversible denaturation” means for enzymes
When an enzyme’s shape is disrupted, its active site may no longer bind substrate effectively. If the underlying polypeptide chain remains largely intact, the enzyme may refold and regain function once conditions return to normal.
Practice Questions
FAQ
Reversibility is often inferred by comparing properties before denaturation, after denaturation, and after recovery conditions are restored.
Common readouts include:
Enzyme activity assays (rate recovery over time)
Spectroscopy changes (e.g., fluorescence shifts)
Thermal shift profiles to estimate $T_m$ changes across treatments
Differences in amino-acid sequence affect folding landscapes.
Key contributors include:
Number/placement of stabilising interactions (salt bridges, hydrophobic core packing)
Domain architecture (single vs multi-domain)
Propensity to form off-pathway intermediates that aggregate
Hysteresis describes a lag or path-dependence where activity does not immediately match restored conditions.
It matters because:
Cells experiencing fluctuating environments may show delayed metabolic recovery
Apparent enzyme “optima” can depend on whether conditions are rising or falling
Disulfide bonds can stabilise folded structure but may also complicate refolding if incorrect disulfides form.
Outcomes depend on:
Whether disulfides remain correctly paired during stress
Presence of cellular catalysts (e.g., isomerases) that reshuffle disulfides to the native pattern
Yes. Subtle misfolding can restore a near-native shape yet distort dynamics essential for catalysis.
Possible effects include:
Reduced turnover ($k_{cat}$) due to altered active-site motions
Altered substrate binding because of small geometry/charge differences
Increased sensitivity to subsequent stress because the refolded state is less stable
