medium · MCAT chem-phys
An enzyme assay is performed at pH 7.4. If the pH is lowered to 5.0 and the enzyme activity is lost, but then restored when the pH is returned to 7.4, what is the most likely cause of the activity loss?
- Permanent hydrolysis of the peptide bonds in the primary structure.
- Irreversible denaturation of the protein tertiary structure.
- Competitive inhibition by excess hydrogen ions at the active site.
- Reversible changes in the ionization states of active-site residues.
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