In enzymology, a prenylcysteine oxidase () is an enzyme that catalyzes the chemical reaction
The 3 substrates of this enzyme are S-prenyl-<small>L</small>-cysteine, O<sub>2</sub>, and H<sub>2</sub>O, whereas its 3 products are prenal, <small>L</small>-cysteine, and H<sub>2</sub>O<sub>2</sub>.
This enzyme belongs to the family of oxidoreductases, specifically those acting on a sulfur group of donors with oxygen as acceptor. The systematic name of this enzyme class is S-prenyl-L-cysteine:oxygen oxidoreductase. This enzyme is also called prenylcysteine lyase.