Gulose as a constituent of a

The extracellular matrix (ECM) of the multicellular green alga VOIW.Y carieri contains insoluble fibrous layers that surround individual cells to form contiguous cellular compartments. A highly sulphated glycoprotein with an apparent molecular mass of 185 kDa (SSG I SS) has been identified as the monomeric precursor of this distinct substructure within the ECM [1,2]. The polypeptide chain of SSG 185 exhibits a central domain consisting almost exclusively of hydroxyproline residues. This central domain is O-glycosylated. Arabinose, mannose and galactose are the main sugar constituents of the saccharides attached to this central domain [1,2]. Exhaustive digestion of SSG 185 with proteases yields a large glycopeptide with an apparent molecular mass of 145 kDa [l]. This protease-resistant fragment represents the central hydroxyproline-rich domain of SSG 185. In this paper, we report the isolation of a small glycopeptide (12 kDa) derived from the 145 kDa fragment. This glycopeptide contains gulose at the non-reducing end, a hexose so far not observed as a constituent of glycoproteins.