Structural Biochemistry/Enzyme/Characteritics of enzyme

Enzymes are proteins (some may be catalytic RNA) that act as catalysts in chemical reactions. They function via a variety of mechanisms, but all increase the rate of reaction by lowering the activation energy of the reaction. Some characteristics of enzymes are as follows:

1. Enzymes are highly specific for a particular substrate. The active site of an enzyme has a strong affinity for a specific substrate, and will slightly change its conformation, known as an "induced fit" to accommodate the target substrate. This induced fit allows for a stabilized transition state, which lowers the activation energy of the reaction.
2. Enzymes remain unchanged during the reaction itself. While the enzyme's amino acid residues may break or form covalent bonds with the substrate, it will typically reform those bonds, enabling the enzyme to react with more substrates.
3. Enzymes are very efficient, catalyzing about 1-10,000 molecules of substrate per second. Therefore, only a small number of enzymes are typically created under normal cellular conditions.
4. Enzymes do not affect the equilibrium constant, or K_eq. While the rate of conversion from substrate to product is increased, the vice versa is true.
5. Enzymes can be allosterically controlled by a variety of means. There are cofactors and coenzymes that are necessary for enzymatic catalysis. Furthermore, there are also molecules that can allosterically inhibit protein function by modifying the conformational shape of the enzyme.
6. Enzymes are affected by pH (acidity or alkalinity) of their surroundings. They are destroyed by strong acid or alkali.