Catalysis of the reaction: H2O + N(8)-acetylspermidine + O2 = 1,3-diaminopropane + 4-acetamidobutanal + H2O2. Also active with N(1)-acetylspermine, weak activity with N(1),N(12)- diacetylspermine.
N(8)-acetylspermidine oxidase (propane-1,3-diamine-forming) activity