The products of chitin degradation, chitosan and chitooligosaccharides, are valuable to the food and agriculture industries. The bio-enzymatic degradation of chitin can overcome the shortcomings of chemical degradation methods. This study identified two novel enzymes involved in chitin degradation from the marine metagenome: chitin deacetylase CDA20 and chitosanase CHIS5. Published chitin deacetylases (CDAs) are generally active against acetylated oligosaccharides with degrees of polymerization ≥ 2 or N-acetyl-d-glucosamine (GlcNAc). However, the deacetylase CDA20 effectively removed the acetyl groups from GlcNAc and chitobiose simultaneously. The chitosanase CHIS5 is an endo-type chitosanase and degraded chitosan into chitooligosaccharides with degrees of polymerization of 2-5. When used in combination, CHIS5 preferentially hydrolyzed chitosan to acetylated chitooligosaccharides, and then CDA20 removed the acetyl group to produce chitooligosaccharides. Our research has identified valuable enzymes related to chitin degradation encoded in the marine metagenome and broadens the theoretical basis for chitin biodegradation by bio-enzymes.,Copyright © 2020 Elsevier Ltd. All rights reserved.