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Why can changes in temperature or pH cause an enzyme to lose its activity?
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catalysis
Nanoparticles of a gold-palladium (yellow-blue) alloy supported on acid-treated carbon (gray) directly catalyzing hydrogen peroxide formation from hydrogen (white) and oxygen (red) while shutting off unwanted hydrogen peroxide decomposition.
Enzymes are specialized proteins whose biological activity depends on a precise three-dimensional structure, which creates a specific active site where reactions occur. Changes in temperature or pH can cause an enzyme to lose its activity because they disrupt the weak noncovalent bondsāsuch as hydrogen bondsāthat maintain this essential shape.1234
When these conditions become extreme, the enzyme undergoes denaturation, a process where the protein unfolds into a looser, more random structure. Because the active site is formed by the protein's specific folding pattern, deforming this site prevents the enzyme from binding to its substrate, thereby eliminating its catalytic ability.42
- Temperature: While reaction rates initially increase with heat, excessive temperatures provide enough energy to break the structural bonds of the enzyme, leading to permanent loss of function. Conversely, extreme cold can also alter an enzyme's shape, causing a loss of activity.3
- pH: Enzymes function most efficiently at an optimum pH. Significant deviations from this level alter the ionization of amino acid side chains, disrupting the internal bonds that hold the enzyme in its functional conformation.345