Bifunctional enzyme that mediates C-3 epimerization of the second intermediate followed by reduction at C-4 during serogroup O11 O-antigen biosynthesis, thus catalyzing the conversion of UDP-N-acetyl-D-glucosamine to precursors for the biosynthesis of O antigen. H(+) + NADH + UDP-2-acetamido-2,6-dideoxy-beta-L-arabino-hex-4-ulose = NAD(+) + UDP-2-acetamido-2,6-dideoxy-beta-L-talose H(+) + NADPH + UDP-2-acetamido-2,6-dideoxy-beta-L-arabino-hex-4-ulose = NADP(+) + UDP-2-acetamido-2,6-dideoxy-beta-L-talose Optimum pH is 9. Bacterial outer membrane biogenesis; LPS O-antigen biosynthesis. Homodimer. Belongs to the NAD(P)-dependent epimerase/dehydratase family.