Isolation and characterization of the major acidic glycosphingolipids from the liver of the English sole (Parophrys vetulus). Presence of a novel ganglioside with a Forssman antigen determinant

Acidic glycosphingolipids of the liver of English sole, Parophrys vetulus, have been isolated and characterized by 1H nuclear magnetic resonance spectroscopy, methylation analysis, and by direct probe electron-impact and fast atom bombardment mass spectrometry. In addition to the acidic glycosphingolipids with known structures (sulfatide, GM4, GM3, GM2, and GD1a), two fractions of a major monosialosylganglioside with TLC mobility slower than GM1 were isolated and characterized as having the following structure. (Formula:q see text). The structure represents a novel combination of a terminal Forssman disaccharide (GalNAc alpha 1----3GalNAc beta 1----3R) and a GM1 ganglioside core linked together. The identity of the terminal Forssman disaccharide was further established by TLC immunostaining with an anti-Forssman monoclonal antibody. This antibody showed strongly positive staining of the ganglioside only after removal of the sialic acid. Thus, the II3NeuAc residue inhibited antibody binding to the terminal disaccharide unit. Analysis of the ceramide moieties of both fractions indicated a predominance of 16:0, 22:1, 22:0, and 24:1 fatty acids in the faster migrating form and 16:0, 18:0, and 18:1 in the slower form in combination with d18:1 sphingosine.