Structural features of sulfated glycans from the tunic of Styela plicata (Chordata-Tunicata). A unique occurrence of L-galactose in sulfated polysaccharides

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Abstract
The sulfated polysaccharides in the tunic of Styela plicata occur as three fractions that differ markedly in molecular mass and chemical composition. The high-molecular-mass fraction has a high galactose content and a strong negative optical rotation while the low-molecular-mass fractions have a higher proportion of amino sugars and glucose. The galactose occurs in these polysaccharides entirely in the L-enantiomeric form. Although L-galatose is a constituent of several polysaccharides, this is the first report of sulfated polysaccharides that contain high amounts of L-galactose, and that lack the D enantiomorph of this sugar. Furthermore, the structure of the high-molecular-mass fraction, which is composed mainly of a core of .alpha.-L-galactopyranose residues, sulfated at position 3, linked glycosidically through position 1 .fwdarw. 4, and with non-sulfated L-galactopyranose non-reducing end-units, is unique among other previously described sulfated glycans. These data are of considerable interest as they show an unusual example of a possible variants of polyanionic glycans with structure function in living tissues.