What are chitin synthases?
The biosynthesis of chitin involves the processive polymerization of GlcNAc units, using activated UDP-GlcNAc as a substrate. Some bacteria related to Rhizobia (and probably some mycorrhizal fungi) possess cytoplasmic oligomer chitin synthases with a limited processivity, typically yielding chitin tetramers or pentamers (which are further processed in these organisms to produce nod- or myc-factors required as signal molecules for the successful establishment of symbioses with plant roots). These enzymes can be used in cell factories for the biotechnological production of chitin oligomers and, in conjunction with chitin deacetylases, of chitosan oligomers. All organisms producing polymeric chitin, such as fungi, insects, crustaceans and other invertebrate animals, possess transmembrane polymer chitin synthases with a much higher processivity, using cytoplasmic UDP-GlcNAc as a substrate and probably secreting the growing chitin chain through a channel formed by the (probably oligomeric) synthase to the outside of the cell where it is integrated into the fungal cell wall or insect cuticle, etc. These polymer chitin synthases are distantly related to cellulose synthases of plants and bacteria with which they probably share a similar biosynthesis mechanism.