Catalyzes the addition of GlcNAc or GlcUA monosaccharides to the nascent hyaluronan polymer. Therefore, it is essential to hyaluronan synthesis a major component of most extracellular matrices that has a structural role in tissues architectures and regulates cell adhesion, migration and differentiation (By similarity). This is one of three isoenzymes responsible for cellular hyaluronan synthesis and it is particularly responsible for the synthesis of high molecular mass hyaluronan (By similarity). [hyaluronan](n) + UDP-N-acetyl-alpha-D-glucosamine = H(+) + N-acetyl-beta-D-glucosaminyl-(1->4)-[hyaluronan](n) + UDP N-acetyl-beta-D-glucosaminyl-(1->4)-[hyaluronan](n) + UDP-alpha-D-glucuronate = [hyaluronan](n+1) + H(+) + UDP Glycan biosynthesis; hyaluronan biosynthesis. Homodimer; dimerization promotes enzymatic activity. Forms heterodimer with HAS3. Forms heterodimer with HAS1. Travels from endoplasmic reticulum (ER), Golgi to plasma membrane and either back to endosomes and lysosomes, or out into extracellular vesicles. Post-translational modifications control HAS2 trafficking. Expressed in corneal endothelial cells. Phosphorylation at Thr-328 is essential for hyaluronan synthase activity. O-GlcNAcylation at Ser-221 increases the stability of HAS2 and plasma membrane localization. Ubiquitination at Lys-190; this ubiquitination is essential for hyaluronan synthase activity and homo- or hetero-oligomerization. Can also be poly-ubiquitinated. Deubiquitinated by USP17 and USP4. USP17 efficiently removes 'Lys-63'- and 'Lys-48'-linked polyubiquitin chains, whereas USP4 preferentially removes monoubiquitination and, partially, both 'Lys-63'- and 'Lys-48'-linked polyubiquitin chain. Belongs to the NodC/HAS family.