In enzymology, a cellobiose dehydrogenase (acceptor) () is an enzyme that catalyzes the chemical reaction cellobiose + acceptor cellobiono-1,5-lactone + reduced acceptor Thus, the two substrates of this enzyme are cellobiose and acceptor, whereas its two products are cellobiono-1,5-lactone and reduced acceptor. This enzyme belongs to the family of oxidoreductases, to be specific those acting on the CH-OH group of donor with other acceptors. The systematic name of this enzyme class is cellobiose:acceptor 1-oxidoreductase. Other names in common use include cellobiose dehydrogenase, cellobiose oxidoreductase, Phanerochaete chrysosporium cellobiose oxidoreductase, CBOR, cellobiose oxidase, cellobiose:oxygen 1-oxidoreductase, CDH, and cellobiose:(acceptor) 1-oxidoreductase. It employs sometimes one cofactor, FAD, but in most cases both a heme and a FAD located in separate domains. It makes the enzyme to one of the more complex extracellular oxidoreductases. It is produced by wood degrading organisms. Structural studies To date, structures of the separated dehydrogenase (DH) and cytochrome (CYT) domains were reported (PDB accession codes and ). In 2015, full-length structures of the enzyme were resolved for CDH from Crassicarpon hotsonii syn. Myriococcum thermophilum (ChCDH, PDB accession code 4QI6) and CDH from Neurospora crassa (NcCDH, PDB accession code 4QI7). The mobility of the CYT domain prevented for a long time the crystallization and X-ray structure elucidation of CDH. However, the crystal structures of the individual CYT and DH domains already showed structural complementarity and the position of the domain interface and provided a structural basis for the interdomain electron transfer observed in biochemical and bioelectrochemical studies. The crystal structure of the Phanerochaete chrysosporium DH domain was described by Hallberg et al. as peanut-shaped with dimensions of ~72 x 57 x 45 Å. The observed GMC-oxidoreductase protein fold features an FAD-binding and a substrate-binding subdomain. The FAD-binding subdomain primarily consists of the Rossmann fold, which is typical for NAD(P)- and FAD-dependent enzymes whereas the substrate-binding subdomain consists of a central twisted, seven-stranded β-sheet with three α-helices on one side of the sheet and the active-site on the other side. The substrate-binding subdomain hosts the active-site that consists of a substrate binding-site (B-site) and the catalytic-site (C-site). The B-site holds the non-reducing end of cellobiose in position whereas at the C-site oxidizes the reducing end of cellobiose. The CYT domain consist of an ellipsoidal antiparallel β-sandwich with dimensions of 30 x 36 x 47 Å and a topology resembling the variable heavy chain of the antibody Fab fragment with a five-stranded inner