Acetylindoxyl is an enzyme that belongs to the family of Oxidoreductase (enzymes that catalyze the transfer of electrons from one molecule, the reductant,  to another, the oxidant) and has two substrates, the N-acetylindoxyl, and oxygen.
Thus, the two substrates of this enzyme are N-acetylindoxyl and oxygen, whereas its product is N-acetylisatin. 
