Enzymsubstrat

Enzymsubstrat, in enzymology, is the molecule that an enzyme acts upon during a chemical reaction. The substrate binds to the enzyme at the active site, forming an enzyme–substrate complex. Through catalysis, the substrate is transformed into one or more products, which are released, allowing the enzyme to catalyze additional turnovers. Substrates are typically defined by their structural complementarity to the enzyme's binding pocket and functional groups that participate in the reaction.

Binding and catalysis: The substrate fits the active site, often via induced fit. Enzymes lower activation energy by stabilizing the transition state. Catalytic strategies include acid-base catalysis, covalent catalysis, metal ion catalysis, and proper orientation of reactive groups.

Specificity and kinetics: Enzymes are selective for their substrates. The concept of a substrate concentration dependence is described by Michaelis-Menten kinetics. The Km reflects affinity, Vmax the maximum rate, and kcat the turnover number. High efficiency occurs when kcat/Km is large.

Examples: Amylase acts on starch to produce smaller sugars; proteases hydrolyze peptide bonds in proteins; lactase hydrolyzes lactose to glucose and galactose; DNA polymerase uses nucleotides as substrates; lipases act on lipids. Some reactions require cofactors or coenzymes; inhibitors or allosteric effectors can alter substrate binding.

Notes: The term enzymsubstrat is used in teaching and literature to describe the substrate of an enzyme. Understanding substrate properties is essential in biochemistry, drug design, and metabolic regulation.