Enzymatic sulfation of gangliotriaosylceramide in human renal cancer cells.

Biosynthesis of sulfoglycolipid is markedly increased in a human renal cancer cell line, SMKT-R3. We investigated the sulfotransferase catalyzing the transfer of sulfate from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to gangliotriaosylceramide (Gg3Cer) in SMKT-R3 cells. On thin-layer chromatography, the reaction product comigrated with Gg3Cer III3-sulfate (SM2b), not with Gg3Cer II3-sulfate (SM2a). To examine which monosaccharide of Gg3Cer was sulfated, the product was treated with beta-hexosaminidase A. Unlike authentic SM2a, of which the non-reducing terminal N-acetylgalactosamine was cleaved off, the product was not hydrolyzed. These results suggest that sulfate was transferred to the non-reducing terminal N-acetylgalactosamine. Gg3Cer sulfotransferase activity was independent of divalent cations but stimulated by Fe2+, and the optimal pH was approximately 6.5. The apparent Km values were 102 microM for PAPS and 348 microM for Gg3Cer. Gg3Cer II3,III3-bis-sulfate (SB2) and a sulfotransferase activity synthesizing SB2 from SM2a were also detected in SMKT-R3 cells.