Functional Analysis of Cellobiose Dehydrogenase from the Saprotrophic Basidiomycete Coprinopsis cinerea

The plant saprophytic fungi including wood rotting fungi secrete various extracellular hydrolytic and oxidative enzymes to degrade wood cell wall. Among these, cellobiose dehydrogenase (CDH) is known as a flavoheme enzyme composed of a flavin domain with FAD and a b-type heme domain. CDH oxidises the reducing end of cellobiose, and transfers electrons to redox partners such as lytic polysaccharide monooxygenases (LPMOs).
Cellobiohydrolase I (CBH I) is the most abundant cellulase produced by filamentous fungi, and recognised as the critical in the degradation of crystalline cellulose. The plant saprophytic basidiomycete Coprinopsis cinerea has been known to possess multiple genes encoding CBH I-like enzyme. However, the CBH I-like enzymes lack family 1 carbohydrate-binding module (CBM1) which has been considered as an essential domain for efficient degradation of crystalline cellulose. Based on the information, it is suggested that the fungus possesses the different mechanism of cellulose degradation with well-studied cellulolytic fungi.
In this study, the gene encoding CDH from C. cinerea (CcCDH) was cloned, and recombinant CcCDH was heterologously produced in the Pichia pastoris expression system. In this presentation, we will discuss the function of CcCDH based on the results of characterisation of the purified recombinant enzyme and the results of three-dimensional structure prediction using the amino acid sequence.