Involved in chitin degradation. Catalyzes the oxidative cleavage of glycosidic bonds in chitin via a copper-dependent mechanism, leading to oxidized chitooligomers with degrees of polymerization of 4-6. Is not active on cellulose. [(1->4)-N-acetyl-beta-D-glucosaminyl]n+m + reduced acceptor + O2 = [(1->4)-N-acetyl-beta-D-glucosaminyl]m-1-(1->4)-2-(acetylamino)-2-deoxy-D-glucono-1,5-lactone + [(1->4)-N-acetyl-beta-D-glucosaminyl]n + acceptor + H2O. Glycan degradation; chitin degradation.