Cellulase

Figure 1. A Cellulase enzyme.

Cellulase is a group of enzymes produced mostly by fungi, bacteria, and protozoans. Cellulases break down the insoluble cellulose molecule ("plant fiber") into soluble monosaccharides ("simple sugars") such as beta-glucose, or shorter polysaccharides and oligosaccharides.

Most mammals have very limited ability to digest dietary fibres like cellulose by themselves. In many mammals, cellulases are produced by symbiotic bacteria that reside within the digestive system. Cellulase is consumed as a dietary supplement primarily to help with digestive problems.