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What happens after an enzyme forms an enzyme-substrate complex?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
A multi-panel diagram illustrates how a substrate binds to an enzyme's active site through induced fit, leading to product formation, and shows how non-substrates and allosteric regulators can alter enzyme activity by binding to different sites on the enzyme.
Enzyme In the induced-fit theory of enzyme-substrate binding, a substrate approaches the surface of an enzyme (step 1 in box A, B, C) and causes a change in the enzyme shape that results in the correct alignment of the catalytic groups (triangles A and B; circles C and D represent substrate-binding groups on the enzyme that are essential for catalytic activity). The catalytic groups react with the substrate to form products (step 2). The products then separate from the enzyme, freeing it to repeat the sequence (step 3). Boxes D and E represent examples of molecules that are too large or too small for proper catalytic alignment. Boxes F and G demonstrate binding of an inhibitor molecule (I and I′) to an allosteric site, thereby preventing interaction of the enzyme with the substrate. Box H illustrates binding of an allosteric activator (X), a nonsubstrate molecule capable of reacting with the enzyme.

After an enzyme forms an enzyme-substrate complex, the enzyme catalyzes a chemical reaction that transforms the substrate into products.12

The specific sequence of events following the formation of this complex includes:

  • Chemical Transformation: The enzyme facilitates the reaction, which may involve the formation of a temporary covalent intermediate or proceed through a single displacement mechanism where the substrate is directly altered. This process lowers the activation energy required for the reaction to occur, allowing it to proceed at a biological rate.12
  • Product Dissociation: Once the chemical transformation is complete, the resulting products dissociate—or separate—from the enzyme's active site.12
  • Regeneration: The enzyme remains unchanged by the reaction. Once the products have been released, the enzyme is free to bind with additional substrate molecules, allowing the cycle to repeat many times per second.12