How does catalase break down hydrogen peroxide?

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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.

Catalase is an enzyme that facilitates the rapid decomposition of hydrogen peroxide into water and oxygen. This chemical reaction is represented by the following equation:

$2 H_{2} O_{2} \to 2 H_{2} O + O_{2}$

By converting this reactive and potentially toxic byproduct of cellular metabolism into harmless substances, the enzyme protects cells from oxidative damage. Located primarily within peroxisomes, catalase ensures that hydrogen peroxide does not accumulate to levels that could harm DNA, proteins, or cell membranes.1