* 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). Cette réaction est essentielle pour protéger les cellules des effets dommageables du peroxyde d'hydrogène, qui est un sous-produit toxique de divers processus cellulaires.

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