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) (PubMed:9760183). Appears to be responsible for synthesis of the majority of the chitin found in the cell wall periphery (PubMed:2050738). It is involved in the synthesis of the chitin ring that forms in the cell wall just before bud emergence (PubMed:2050738). This ring remains at the base of the bud as the bud grows and ultimately forms part of the bud scar marking the division site on the mother cell (PubMed:2050738). Also catalyzes the synthesis of chitin laid down during mating and spore cell-wall synthesis (PubMed:2050737, PubMed:2050738, PubMed:1293886). [(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 Homodimer (PubMed:28346351). May form higher order oligomers (PubMed:28346351). Seems to interact with BNI4 and SKT5 which link CHS3 to septins (PubMed:9314530, PubMed:28346351). Localizes to a ring on the surface of cells about to undergo bud emergence and in the mother-bud neck of small-budded cells (PubMed:8909536). Delocalized throughout the plasma membrane during heat shock (PubMed:12928491). Also localizes to intracellular membrane-bound particles called chitosomes, proposed to act as a reservoir for regulated transport of chitin synthase enzymes to the division septum (PubMed:8970154, PubMed:12928491). Glycosylated. Palmitoylated by PFA4; required for proper export from the ER. Decreases cell wall chitin level (PubMed:28346351). Resistance to Calcofluor White (cell wall stressor) (PubMed:28346351). Decreases conjugation frequency (PubMed:9234668). Present with 1510 molecules/cell in log phase SD medium. Belongs to the chitin synthase family. Class IV subfamily. Was originally thought that the N- and C-termini were extracellular (PubMed:16847258). However, more recent data suggests that the N- and C-termini are cytoplasmic (PubMed:28346351).