Metagenomic mining and molecular characterization of a psychrophilic GH5-CBM5 cellulase from Krossfjorden sediments, Arctic

The polar regions are gaining attention as a source of cold-active microorganisms with potential genetic resources. Arctic fjord environments have proven to be reservoirs of diverse microbial communities, with enzymatic activities adapted to maintain cellular functions at low temperatures. These psychrophilic enzymes have wider industrial applications than their mesophilic forms. The current study reports a cold-active cellulase (Cell-KRD) from the Krossfjorden sediment metagenome by PCR-based screening. The enzyme structure reveals that the Cell-KRD has a catalytic module (CM) belonging to the GH5_2 subfamily, which is connected to a carbohydrate-binding module (CBM5) by a much longer linker sequence (LS) than its mesophilic counterparts. The CM of Cell-KRD (GH5_2 subfamily) exhibits a (β/α)₈ topology structure which consists of a catalytic cleft and a substrate binding pocket. Cell-KRD showed similar features with that of psychrophilic cellulases compared to their mesophilic and thermophilic homologues. In silico analyses, including molecular docking studies revealed the significant features of Cell-KRD, which enable efficient cellulose hydrolysis in cold environments.