Enzimi

Enzymes are biological catalysts that accelerate chemical reactions in living organisms. Most enzymes are proteins, although a small class of RNA molecules, known as ribozymes, also have catalytic activity. Enzymes work by lowering the activation energy of a reaction, the energy barrier that must be overcome for reactants to be converted into products. In doing so, they increase reaction rates without being consumed in the process.

Each enzyme binds a specific set of molecules called substrates, usually at a region called the active site. Binding is highly selective, and many enzymes undergo an induced fit when the substrate binds. Enzymatic activity is commonly described by Michaelis-Menten kinetics, with Km reflecting substrate affinity and Vmax the maximum rate. The turnover number, kcat, measures how many substrate molecules are converted per enzyme per unit time.

Enzymes require cofactors such as metal ions or organic molecules called coenzymes, often derived from vitamins. They can be regulated by inhibitors and cellular signals. Inhibitors may be competitive, noncompetitive, or uncompetitive, altering binding or catalysis. Enzyme activity is also influenced by temperature and pH, with each enzyme having optimal conditions; deviations can reduce activity or denature the protein. Allosteric regulation and feedback inhibition provide control within metabolic networks.

Enzymes play essential roles in digestion, metabolism, DNA replication, and many industrial processes. Common examples include amylase, proteases such as pepsin, lipase, and lactase. In biotechnology and medicine, enzymes are used in diagnostics, therapeutics, food production, and detergents, illustrating their broad practical importance.