Cellulosesynthase

Cellulosesynthase is an enzyme that catalyzes the polymerization of glucose units to form cellulose, a primary component of plant and some microbial cell walls. In plants and many algae, it is responsible for producing the β-1,4-glucan chains that assemble into crystalline cellulose microfibrils, which provide structural strength and integrity to the cell wall. In many bacteria, a distinct cellulose synthase system also generates extracellular cellulose as part of biofilms and protective matrices.

Biochemically, cellulosesynthase uses UDP-glucose as the activated sugar donor to add glucose units to a growing cellulose chain in a processive manner. The catalytic subunit is typically a membrane-associated glycosyltransferase that resides in the plasma membrane, often organized into multi-subunit complexes known as cellulose synthase complexes. These complexes extrude newly formed cellulose chains into the cell wall space, where they aggregate into microfibrils. The enzyme is usually encoded by a family of related genes, with different paralogs contributing to tissue-specific expression and developmental regulation in plants.

In plants, cellulose synthase proteins commonly contain transmembrane domains at their N- and C-termini and a central cytosolic catalytic domain, classed within glycosyltransferase family 2. The activity and targeting of cellulosesynthase are tightly regulated by signaling pathways, cytoskeletal dynamics, and vesicle trafficking, ensuring proper deposition of cellulose during cell growth and differentiation.

The enzyme is essential for organismal form and function: it underpins cell wall rigidity, determines tissue mechanics, and influences growth, crop yield, and biomass properties. Disruptions in cellulosesynthase can lead to weak cell walls, altered morphology, or compromised biofilm formation in microbes.