hyaluronan synthase activity
alternating UDP-alpha-N-acetyl-D-glucosamine:beta-D-glucuronosyl-(1,3)- 4-N-acetyl-beta-D-glucosaminyltransferase and UDP-alpha-D-glucuronate:N-acetyl-beta-D-glucosaminyl-(1,4)- 3-beta-D-glucuronosyltransferase activity