A trisialosyl ganglioside GT3 of hog kidney. Structure and biosynthesis in vitro

A trisialosyl ganglioside was isolated from hog kidney cortex and purified with a yield of 6.8 nmol/g tissue or 13 mol % of total gangliosides. The homogeneous ganglioside was subjected to graded neuraminidase treatment, mild acid hydrolysis, periodate oxidation-borohydride reduction, permethylation analysis and chromium trioxide oxidation. The results suggested that the structure of this ganglioside is NeuAc alpha 2-8NeuAc alpha 2-8NeuAc alpha 2-3Gal beta 1-4Glc beta 1-1Cer (GT3). On the addition of exogenous disialosyl ganglioside GD3 and radioactive CMP-NeuAc, a GT3 synthesis activity was demonstrated in a crude membrane fraction of hog kidney. The activity was greatest in the presence of detergents and had a pH optimum of 6.4. Apparent Km values for CMP-NeuAc and GD3 were about 0. 6 and 0.1 mM, respectively. The reaction produce was assigned as GT3 by chromatographic separation, carbohydrate analysis and periodate oxidation followed by borohydride reduction.