* Substrate: Catalase's substrate is hydrogen peroxide (H₂O₂). This is a toxic byproduct of cellular metabolism.

* Shape: Catalase is a tetrameric enzyme, meaning it consists of four protein subunits. Each subunit has a globular shape and contains a heme prosthetic group, which is essential for its catalytic activity. The overall shape of the catalase enzyme is spherical or ovoid.

How Catalase Works:

1. Binding: Hydrogen peroxide binds to the heme group within the catalase molecule.

2. Catalysis: The heme group, containing iron, facilitates the breakdown of hydrogen peroxide into water (H₂O) and oxygen gas (O₂).

3. Release: The products are released, and the catalase enzyme is ready to catalyze another reaction.

Important Note: The shape of catalase is crucial for its function. The specific shape allows for the binding of hydrogen peroxide at the active site and facilitates the chemical reaction that breaks it down.