Glycoside hydrolase family 113 beta-1,4-mannanase and similar proteins. Mannan endo-1,4-beta mannosidase (E.C 3.2.1.78) randomly cleaves (1->4)-beta-D-mannosidic linkages in mannans, galactomannans and glucomannans and is also called beta-1,4-mannanase, endo-1,4-beta-mannanase, endo-beta-1,4-mannase, beta-mannanase B, beta-1, 4-mannan 4-mannanohydrolase, endo-beta-mannanase, beta-D-mannanase, 1,4-beta-D-mannan mannanohydrolase, and 4-beta-D-mannan mannanohydrolase. (1->4)-beta-linked mannans are polysaccharides with a linear polymer backbone of (1->4)-beta-linked mannose units (in plants and fungi) or alternating mannose and glucose/galactose units (glucomannan in plants and fungi, and galactomannan and galactoglucomannan in plants), such as in the hemicellulose fraction of hard- and softwoods. Complete degradation of mannan requires a series of enzymes, including beta-1,4-mannanase. According to the CAZy database beta-1,4-mannanases are grouped into various glycoside hydrolase (GH) families; GH family 113 beta-1,4-mannanases include mostly bacterial and archaeal sequences.