In enzymology, putrescine oxidase () is an enzyme that catalyzes the chemical reaction
The 3 substrates of this enzyme are putrescine, water, and oxygen. Its products are 4-aminobutanal, hydrogen peroxide, and ammonia.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-NH<sub>2</sub> group of donors with oxygen as acceptor. The systematic name of this enzyme class is putrescine:oxygen oxidoreductase (deaminating). This enzyme participates in urea cycle and metabolism of amino groups. It employs one cofactor, FAD.