Britannica Sources used in this answer

How does adrenaline activate enzymes that help cells produce energy?

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.

Adrenaline (epinephrine) activates enzymes involved in energy production through a signaling cascade that utilizes a second messenger system.1

When adrenaline binds to beta-adrenergic receptors on the surface of a cell, it triggers the activation of G-proteins, which in turn stimulate the enzyme adenylyl cyclase. This enzyme catalyzes the conversion of cellular components into cyclic adenosine monophosphate (cAMP).12

Acting as a second messenger, cAMP propagates the signal throughout the cell and activates various enzymes responsible for metabolizing carbohydrates to produce energy. For instance, this pathway stimulates glycogenolysis, the process by which stored glycogen is broken down into glucose. The resulting glucose-6-phosphate can then enter glycolysis, a series of reactions that captures and stores energy in the form of adenosine triphosphate (ATP). Through this mechanism, adrenaline ensures that cells have rapid access to the fuel necessary to meet increased energy demands, such as those experienced during a fight-or-flight response.1234