UDP-glycosyltransferase activity hexosyltransferase activity hyaluronan synthase activity https://github.com/geneontology/go-ontology/issues/30193 MetaCyc:2.4.1.212-RXN spHAS EC:2.4.1.212 seHAS alternating UDP-alpha-N-acetyl-D-glucosamine:beta-D-glucuronosyl-(1,3)-[nascent hyaluronan] 4-N-acetyl-beta-D-glucosaminyltransferase and UDP-alpha-D-glucuronate:N-acetyl-beta-D-glucosaminyl-(1,4)-[nascent hyaluronan] 3-beta-D-glucuronosyltransferase activity HAS activity molecular_function RHEA:12528 GO:0050501 Reactome:R-HSA-2160851 alternating UDP-alpha-N-acetyl-D-glucosamine:beta-D-glucuronosyl-(1->3)-[nascent hyaluronan] 4-N-acetyl-beta-D-glucosaminyltransferase and UDP-alpha-D-glucuronate:N-acetyl-beta-D-glucosaminyl-(1->4)-[nascent hyaluronan] 3-beta-D-glucuronosyltransferase activity Catalysis of the reaction: UDP-D-glucuronate + UDP-N-acetyl-D-glucosamine = [beta-N-acetyl-D-glucosaminyl-(1->4)-beta-D-glucuronosyl-(1->3)](n) + 2n UDP.