Cellobiose dehydrogenase (CHD; EC:1.1.99.18) is found in a variety of fungi, including white rot, brown rot and plant pathogen fungi. The enzyme is the only known extracellular flavocytochrome and it degrades both cellulose and lignin. Specifically, CDHs oxidise cellobiose, cellodextrins, and lactose to corresponding lactones, utilising a variety of electron acceptors PMID:16787264. It comprises two domains: a cytochrome domain containing a b-type haem, which is linked through a peptide linker to a large flavodehydrogenase domain containing FAD as a cofactor PMID:9920875. The two domains can be separated proteolytically to yield a functional cytochrome and a flavodehydrogenase PMID:10673428.

This superfamily represents the b-type cytochrome domain. This domain assumes an immunoglobulin-like beta-sandwich fold consisting of 7 beta-strands in 2 sheets with a Greek key topology; the haem iron is ligated by a Met/His couple and is docked at the exterior of the enzyme PMID:10673428. It is found at the N-terminus of these enzymes, and belongs to the DOMON domain superfamily, a ligand-interacting motif found in all three kingdoms of life PMID:17878204.

PFAM:PF16010, INTERPRO:IPR015920,DOI:10.1016/S0969-2126(00)00082-4