Defructosylated K4 Polysacchar

K4 polysaccharide is a capsular polysaccharide produced by the E. coli K4 strain, bearing a backbone composed of [→4)-β-D-glucuronic acid (GlcA)-(1→3)-N-acetyl-β-D-galactosamine (GalNAc)-(1→]n with a β-D-fructofuranose branched at C-3 of GlcA. Defructosylated K4 polysaccharide is derived from K4 polysaccharide by defructosylation. Because it has the same structure as that of chondroitin, it can be used as the substrate in biosynthesis of chondroitin sulfate (CS), a widely used dietary supplement for treatment of osteoarthritis and an important glycosaminoglycan (GAG) with multiple bioactivities founded in the human body. Therefore, defructosylated K4 polysaccharide offers a promising precursor for preparation of a bioengineered CS using an enzymatic combinatorial approach, and generation of all kinds of substrates for the enzymes involved in the biosynthesis/chemosynthesis of chondroitin, dermatan and their sulfated derivatives. Furthermore, as a good substrate, defructosylated K4 polysaccharide can be degraded by chondroitinase ABC I into oligosaccharide with Δ4,5GlcA at the non-reducing end which can be detected by UV spectroscopy at 232 nm.