chitin synthase activity EC:2.4.1.16 Catalysis of the reaction: UDP-N-acetyl-D-glucosamine + [->4)-N-acetyl-beta-D-glucosaminyl-(1-](n) = UDP + [->4)-N-acetyl-beta-D-glucosaminyl-(1-](n+1). GO:0004100 chitin-uridine diphosphate acetylglucosaminyltransferase activity MetaCyc:CHITIN-SYNTHASE-RXN trans-N-acetylglucosaminosylase activity chitin synthetase activity molecular_function UDP-N-acetyl-D-glucosamine:chitin 4-beta-N-acetylglucosaminyl-transferase activity chitin-UDP N-acetylglucosaminyltransferase activity chitin-UDP acetyl-glucosaminyl transferase activity acetylglucosaminyltransferase activity