Cellulosome

Cellulosomes are multi-enzyme complexes. The cellulosomes are associated with the cell surface and mediate cell attachment to the insoluble substrate and degrade it to soluble products which are then absorbed. Cellulosome complexes are intricate multi-enzyme machines produced by many cellulolytic microorganisms (cellulosome producing bacteria are listed below). They are designed by the microorganisms for efficient degradation of plant cell wall polysaccharides, notably cellulose—the most abundant organic polymer on Earth. The multiple subunits of cellulosomes are composed of numerous functional domains which interact with each other and with the cellulosic substrate. One of these subunits, a large glycoprotein, which we called "scaffoldin", comprises a distinctive new class of non-catalytic scaffolding polypeptide. The scaffoldin subunit selectively integrates the various cellulases and xylanase subunits into the cohesive complex, by combining its "cohesin" domains with a typical "dockerin" domain present on each of the subunit enzymes. The scaffoldin of some cellulosomes, an example being that of C. thermocellum, contains a carbohydrate-binding module that adheres cellulose to the cellulosomal complex.