Enzymy

Enzymy are biological catalysts that accelerate chemical reactions in living organisms. They are typically proteins, though some RNA molecules, called ribozymes, also have catalytic activity. Enzymes work by lowering the activation energy of a reaction, allowing it to proceed more rapidly than it would otherwise. Each enzyme binds specific substrates at its active site, a region whose shape and chemistry are complementary to the substrates.

Enzyme mechanisms often involve precise interactions within the active site. Two common ideas are the lock-and-key model, where the substrate fits the enzyme exactly, and the induced-fit model, where the enzyme changes shape upon binding. Many enzymes require non-protein helpers, such as metal ions or organic molecules known as coenzymes; some carry permanent cofactors or prosthetic groups.

Enzymes are classified into six major groups based on the type of reaction they catalyze: oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases. Kinetic traits are described by the Michaelis–Menten framework, including Km, which reflects substrate affinity, and Vmax, the maximum velocity. Enzyme activity is modulated by temperature, pH, and the presence of inhibitors (competitive, noncompetitive) or activators. Regulation often occurs through allosteric control and feedback inhibition, enabling coordination of metabolic pathways.

Biological importance and applications: enzymes drive digestion, metabolism, DNA replication, and signaling processes. They have broad industrial and medical uses, including food processing, biotechnology, diagnostic assays, and enzyme replacement therapies. Understanding enzyme function is essential to fields ranging from physiology to pharmacology and industrial biocatalysis.