Figure 2.

Schematic representation of an in vitro pathway to produce the unique red-algal sugar 3,6-anhydro-D-galactose from ι- and κ-carrabiose containing galactans. Inspired by the carrageenan degradation in marine heterotrophic bacteria, the pathway consists of an initial depolymerization step to yield neocarrageenan oligosaccharides, which are further desulfated by the action of specific sulfatases to form nonsulfated oligosaccharides. These oligosaccharides are further monomerized by a combination of galactosidases to yield DA and D-gal.