Structural investigations of the galactan of the snail Lymnaea stagnalis

Abstract A galactan, isolated from the spawn of the snail Lymnaea stagnalis , contained d -galactose and 0.9% of nitrogen, but neither l -galactose nor phosphate groups. The [α] D 20 values of the galactan and its first Smith-degradation product were +19.5° and +20°, respectively. During each of two consecutive Smith-degradations of the galactan, 1 mol of periodate was consumed and 0.45 mol of formic acid was liberated per mol of “anhydrogalactose” unit. Methylation analyses of the galactan and its first Smith-degradation product yielded equal proportions of 2,3,4,6-tetra- O -methyl- and 2,4-di- O -methyl-galactose. Only small quantities of 2,4,6- (4.9 mol%) and 2,3,4-tri- O -methylgalactose (0.7 mol%) were formed from the galactan, whereas the first Smith-degraded product gave 15.6 and 20.4 mol%, respectively. The product of the second Smith-degradation disintegrated and the following oligosaccharides were identified: β- d -Gal-(1→1)- l -Gro, β- d -Gal-(1→3)-β- d -Gal-(1→1)- l -Gro, β- d -Gal-(1→6)-β- d -Gal-(1→1)- l -Gro, β- d -Gal-(1→6)- d -Gal-β- d -Gal-(1→3)-β- d -Gal-(1→1)- l -Gro, β- d -Gal-(1→3)-[β- d -Gal-(1→6)]-β- d -Gal-(1→1)- l -Gro, β- d -Gal-(1→3)-β- d -Gal-(1→6)-β- d -Gal-(1→1)- l -Gro, and β- d -Gal-(1→3)-β- d -Gal-(1→3)-β- d -Gal-(1→1)- l -Gro. Thus, the galactan is highly branched with the backbone containing sequences of either exclusively (1→6)-linked or of more or less regularly alternating (1→3)- and (1→6)-linked units. The side chains vary in length and in the degree of branching. In immunoprecipitin studies, a high degree of species-specificity was seen when various snail galactans were tested with the antiserum to the Lymnaea stagnalis galactan.