How can enzymes be unfolded

The thermostability of an enzyme that exhibits phytase and acid phosphatase activities was studied. Kinetics of inactivation and unfolding during thermal denaturation of the enzyme were compared. If proteins in a living cell are denatured, this results in disruption of cell activity and possibly cell death. Denatured proteins can exhibit a wide range of characteristics, from conformational change and loss of solubility to aggregation due to the exposure of hydrophobic groups.

Enzyme denaturation is normally linked to temperatures above a species' normal level; as a result, enzymes from bacteria living in volcanic environments such as hot springs are prized by industrial users for their ability to function at high temperatures, allowing enzyme-catalyzed reactions to be operated at a very high rate. There are different types of inhibitors. Competitive inhibitors bind to and block the enzymes active site. Non-competitive inhibitors bind to a site other than the active site, but cause the active site to be non-functional.

The atoms in enzymes normally vibrate, but not so much that the molecule unfolds. Increasing the temperature of the enzyme increases the amount of vibration. Too much jiggling and the enzyme begins to lose its proper shape. Enzymes have an optimal temperature range in which they are most active. Enzyme activity increases as the temperature reaches this optimum range, but sharply decreases after this range is passed.

Most animal enzyme lose activity above 40 degrees Celsius. There are bacteria called extremophiles that can survive in hot springs. Pepsin, the enzyme that breaks down protein in the stomach, only operates at a very low pH. The stomach maintains a very low pH to ensure that pepsin continues to digest protein and does not denature. Because almost all biochemical reactions require enzymes, and because almost all enzymes only work optimally within relatively narrow temperature and pH ranges, many homeostatic mechanisms regulate appropriate temperatures and pH so that the enzymes can maintain the shape of their active site.

It is often possible to reverse denaturation because the primary structure of the polypeptide, the covalent bonds holding the amino acids in their correct sequence, is intact. Once the denaturing agent is removed, the original interactions between amino acids return the protein to its original conformation and it can resume its function.

However, denaturation can be irreversible in extreme situations, like frying an egg. The heat from a pan denatures the albumin protein in the liquid egg white and it becomes insoluble.