The process of metabolism involves a large number of enzymes, which are regulated in many ways. They control the rate of reaction by catalyzing the conversion of one chemical into another. In addition to their catalytic activity, enzymes are also regulated by pH and location within the cell. Many molecules in the cell inhibit enzymes, either competitively or noncompetitively. Enzymes are also regulated by activators, which enhance their function allosterically.
Enzymes are complex proteins. They help break down food particles and convert them into usable sugars. Some enzymes play important roles in the human body, such as amylase, which breaks down starch into sugars. Others, such as thrombin, help promote wound healing. Some enzymes also play a role in the process of cellular respiration, while others are responsible for destroying cell walls and killing bacteria.
Enzymes bind to substrates through a highly specific interaction. The substrate binds to an enzyme’s active site, a cleft or groove on the surface of the enzyme. These active sites are formed by amino acids from different polypeptide chains. The amino acids in the active site interact with each other through a variety of chemical, ionic, and hydrophobic interactions. These interactions create a unique chemical environment for the enzyme to function.
Enzymes also lower the activation energy of chemical reactions occurring inside the cell. The enzymes work by binding to the reactant molecules and holding them in place to facilitate the chemical bond-breaking or bond-forming process. The catalytic activity of enzymes requires coenzymes, which are low-molecular-weight organic molecules that work with enzymes. Inhibitors reduce the catalytic activity of enzymes by hindering their ability to attach to a substrate.
Enzymes play a key role in biochemical reactions, providing optimum conditions for metabolic processes. Generally, an enzyme catalyzes the first step in a biochemical pathway. In some cases, the enzyme’s activity is controlled by binding to regulatory molecules in allosteric sites, which are sites other than the active site. The binding changes the enzyme’s structure and makes it active or inactive.
Allosteric inhibition is another type of regulation. The inhibitor binds to a regulatory site outside the active site. This changes the enzyme’s conformation to promote the conversion of a substrate to another. Depending on the type of substrate, this process may cause the enzyme to alter its shape, thereby enhancing its catalytic activity.
In a metabolic pathway, several enzymes catalyze the same reactions. During feedback inhibition, the end product of one reaction inhibits an enzyme at another step. This is a major regulatory mechanism in cells. Feedback inhibition helps cells control their production by limiting the number of enzymes that are active in the next step.
In enzymes, the active site includes a pocket where specific amino acids bind. Chymotrypsin’s binding pocket contains hydrophobic amino acids that interact with the hydrophobic side chains of its preferred substrates. Trypsin’s binding pocket contains negatively charged aspartate residues, which are associated with a negative charge.