preferred_name: a 3-O-[beta-D-galactosyl-(1->3)-N-acetyl-alpha-D-galactosaminyl]-L-seryl-[protein] + 3'-phosphoadenylyl sulfate <=> a 3-O-[3'-O-sulfo-beta-D-galactosyl-(1->3)-N-acetyl-alpha-D-galactosaminyl]-L-seryl-[protein] + adenosine 3',5'-bisphosphate + H(+)