* Endoenzymes work *inside* the cell where they are produced. They catalyze reactions within the cell's internal environment.

* Exoenzymes are secreted *outside* the cell where they are produced. They break down large molecules in the external environment.

Catalase is found within the peroxisomes of cells. Its primary function is to break down hydrogen peroxide (H₂O₂) into water (H₂O) and oxygen (O₂). This reaction is essential to protect cells from the damaging effects of hydrogen peroxide, which is a toxic byproduct of various cellular processes.

Since catalase works within the cell, it is classified as an endoenzyme.