Polymerizes chitin, a structural polymer of the cell wall and septum, by transferring the sugar moiety of UDP-GlcNAc to the non-reducing end of the growing chitin polymer (Probable). Involved in mating tube and dikaryotic hyphae formation and required for the formation of invading hyphae during plant infection (PubMed:16314447). [(1->4)-N-acetyl-beta-D-glucosaminyl](n) + UDP-N-acetyl-alpha-D-glucosamine = [(1->4)-N-acetyl-beta-D-glucosaminyl](n+1) + H(+) + UDP A constitutive cytoplasmic pool is present that localizes to intracellular microvesicles termed chitosomes. Chitosomes constitute a separate secretory route distinct from the typical secretory pathway and serve as a vehicle for delivering the enzyme to the sites on the cell surface where polysaccharide sythesis takes place. Localizes to septa of yeast-like cells and to the basal septum separating the living tip cell from the vacuolated part in hyphae. Also localizes to the growing bud tip in yeast-like cells and in a tip-ward gradient at the hyphal apex. In the N-terminal section; belongs to the TRAFAC class myosin-kinesin ATPase superfamily. Myosin family. In the C-terminal section; belongs to the chitin synthase family. Class V subfamily.