Enzymesubstrate

Enzyme-substrate interaction refers to the binding of a substrate to an enzyme's active site, forming an enzyme–substrate complex that enables the chemical transformation. The specificity arises from complementary shape, charge, and chemical properties; models include lock-and-key and induced-fit, the latter allowing conformational changes that improve fit during binding. The binding lowers the activation energy by stabilizing the transition state and providing catalytic groups that participate in the reaction. The rate depends on substrate concentration and enzyme kinetics; under Michaelis-Menten kinetics, the apparent Km indicates affinity; Vmax is the maximum rate at saturating substrate; kcat is turnover number; catalytic efficiency is kcat/Km.

Complex regulation: inhibitors can be competitive or noncompetitive; allosteric effectors modulate activity; cofactors and coenzymes (such as metal ions, NAD+, ATP) can enable or enhance catalysis. Temperature and pH impact substrate binding and catalytic residues; extreme conditions can denature enzymes. Substrate specificity means an enzyme acts on a limited set of substrates, determined by active site geometry and chemistry.

Examples: digestive enzymes such as sucrase catalyze hydrolysis of sucrose; proteases break down peptides; polymerases catalyze formation of nucleic acids using substrates DNA or RNA nucleotides.

Importance: enzymes accelerate biological reactions, control metabolic pathways, and are central to physiology and industry. Alterations in enzyme-substrate interactions underlie many diseases and are targets for drugs, such as enzyme inhibitors used in therapeutics.