DOMON-like type 9 carbohydrate binding module. Family 9 carbohydrate-binding modules (CBM9) play a role in the microbial degradation of cellulose and hemicellulose (materials found in plants). The domain has previously been called cellulose-binding domain. The polysaccharide binding sites of CBMs with available 3D structure have been found to be either flat surfaces with interactions formed by predominantly aromatic residues (tryptophan and tyrosine), or extended shallow grooves. CBM9 domains found in this uncharacterized heterogeneous subfamily are often located at the C-terminus of longer proteins and may co-occur with various other functional domains such as glycosyl hydrolases. The CBM9 module in these architectures may be involved in binding to carbohydrates.

Domon-like ligand-binding domains. DOMON-like domains can be found in all three kindgoms of life and are a diverse group of ligand binding domains that have been shown to interact with sugars and hemes. DOMON domains were initially thought to confer protein-protein interactions. They were subsequently found as a heme-binding motif in cellobiose dehydrogenase, an extracellular fungal oxidoreductase that degrades both lignin and cellulose, and in ethylbenzene dehydrogenase, an enzyme that aids in the anaerobic degradation of hydrocarbons. The domain interacts with sugars in the type 9 carbohydrate binding modules (CBM9), which are present in a variety of glycosyl hydrolases, and it can also be found at the N-terminus of sensor histidine kinases.

alpha-beta barrel catalytic domain of agarase, such as GH86-like endo-acting agarases identified in non-marine organisms. Typically, agarases (E.C. 3.2.1.81) are found in ocean-dwelling bacteria since agarose is a principle component of red algae cell wall polysaccharides. Agarose is a linear polymer of alternating D-galactose and 3,6-anhydro-L-galactopyranose. Endo-acting agarases, such as glycoside hydrolase 16 (GH16) and GH86 hydrolyze internal beta-1,4 linkages. GH86-like endo-acting agarase of this protein family has been identified in the human intestinal bacterium Bacteroides uniformis. This acquired metabolic pathway, as demonstrated by the prevalence of agar-specific genetic cluster called polysaccharide utilization loci (PULs), varies considerably between human populations, being much more prevalent in a Japanese sample than in North America, European, or Chinese samples. Agarase activity was also identified in the non-marine bacterium Cellvibrio sp.

Endo-1,4-beta-xylanase, GH35 family [Carbohydrate transport and metabolism].

Beta-glucosidase/6-phospho-beta-glucosidase/beta-galactosidase [Carbohydrate transport and metabolism].