Can denature enzymes from the cold

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Denaturation of proteins by temperature

Almost all proteins are irreversibly denatured and precipitated by heat, because the proteins aggregate on cooling or can only partially or not at all fold back into their native conformation with the formation of new internal hydrogen bonds.

When the temperature rises, a number of intramolecular interactions are affected. First of all, this concerns the interactions between more distant areas of the polypeptide chain (long-range-Interactions) that are essential for maintaining the tertiary structure. The protein becomes more flexible and, as a result, amino acid residues that are located further inside also normally end up on the surface of the protein. This process is still reversible. With further heating, the internal hydrogen bridges are released, helical structures break open and the amino acids form hydrogen bonds with water molecules. The protein unfolds more and more. The native conformation cannot be regained because the newly formed, incorrect hydrogen bonds would have to be completely broken before the correct folding can take place - and this is extremely unlikely. The protein is now irreversibly denatured.

Most proteins are very sensitive to temperature increases and are therefore routinely cleaned at 0 to. But there are exceptions here as well: some proteins are extremely stable at high temperatures or even denature in the cold. These extremely heat-stable proteins include, for example, some enzymes of thermophilic archaea that do not denature even at temperatures above. This can then easily be used for protein isolation by heating the protein mixture and thereby denaturing and precipitating all proteins that are not heat-stable.