Catalyzes the biosynthesis of UDP-sulfoquinovose by the transfer of sulfite to UDP-glucose (PubMed:22059775, PubMed:25605538). Important for the assembly of the S-layer N-glycans (PubMed:22059775). The reaction probably occurs through an NAD(+)-dependent oxidation/dehydration/enolization/sulfite addition process (PubMed:25605538). In vitro, in the absence of sulfite, UDP-D-glucose is converted via UDP-4-keto-D-glucose to UDP-D-glucose-5,6-ene (PubMed:25605538). H(+) + sulfite + UDP-alpha-D-glucose = H2O + UDP-alpha-D-6-sulfoquinovose Deletion of the gene results in a significant change in the size of the S-layer SlaA and the flagellin FlaB glycoproteins. Mutant has a significantly lower growth rate at elevated salt concentrations. Belongs to the NAD(P)-dependent epimerase/dehydratase family.