Antitumor Peptidoglycan with New Carbohydrate Structure from Squid Ink

Squid ink, which has little commercial use and is usually discarded, was extracted with Tris-HCl buffer (pH 6.8). The extract was fractionated using DEAE Sephacel ion-exchange chromatography and Sephacryl S-300gel filtration to give a peptidoglycan fraction that exhibited strong antitumor activity against Meth-A fibrosarcoma in BALB/c mice following intraperitoneal injection. The fraction contained 17.8% peptide, 51.2% polysaccharide moiety, and 30.3% pigment. Furthermore three fucose (Fuc)-rich glycosaminoglycans (GAGs), illexin (ILX)-A, -B, and -C (MW 50000, 50000–80000, and 80000), were isolated from the peptidoglycan fraction, using Actinase E digestion, DEAE Sephadex A-50 ion-exchange chromatography, and Sephacryl S-300gel filtration. They gave a single band on the electrophoresis using cellulose acetate membrane and contained equimolar ratios of Fuc, glucuronic acid (GlcA), and N-acetylgalactosamine (GalNAc). These GAGs were not digested with any glycosaminoglycanases, but each gave tri- and hexasaccharides with mild acid hydrolysis. On the basis of spectral data, chemical compositional analysis, and chemical and enzymatic degradation analyses of GAGs and the pyridylaminated (PA) oligosaccharides, the unique repeating branched-structure of the GAGs was determined to be [-3GlcAβl-4(GalNAcαl-3)Fucαl-]n.