Presence and characterization of glycolipid sulfotransferase in human cancer serum (original) (raw)

1990, European Journal of Biochemistry

Sulfotransferase, which catalyzes sulfation of the carbohydrate of galactosylceramide (GalCer) and is localised in the Golgi membrane of cells, was assayed for activity in human serum. To do this, an organic solvent was added to the incubated reaction mixture containing GalCer as an acceptor and phosphoadenosine p h~s p h o [~ sulfate as a donor of sulfate to dissociate the synthesized sulfolipid from serum protein. This was followed by isolation of the sulfolipid on an anion-exchange column. Through this procedure, human serum was found to contain sulfotransferase activity. The serum enzyme was activated by Mn2+. K, values of the enzyme for GalCer and 'active sulfate' were 4.6 pM and 5.2 pM, respectively. The enzyme activity was assayed in sera of cancer patients. The serum activity (mean 5 SE, 0.27 0.027 pmol. pl-'. h-l) in renal cell carcinoma patients, whose activity has been demonstrated to be elevated, was significantly (P < 0.005) increased compared to that of the normal control (mean SE, 0.18 f 0.0014 pmol. pl-'. h-') and of other urological tumors examined. Cerebroside sulfotransferase transfers a sulfate group from 3'-phosphoadenosine 5'-phosphosulfate (PAdoPS) to C3 of the galactose moiety of GalCer to form a sulfolipid [l]. The sulfotransferase activity was demonstrated in particulate fractions from brains of rat [2-41, sheep [5] and mouse [6,7] and in the Golgi apparatus from rat brain [8] and rat kidneys [9-111. The localization of cerebroside sulfotransferase is similar to that of glycosaminoglycan sulfotransferases [12] and tyrosylprotein sulfotransferase [13], but different from that of sulfotransferases acting on aryl compounds, hydroxysteroids, estrogens, and bile acids [14], all ofwhich are found in cytosol. Glycosyltransferase activity catalyzing glycolipid synthesis is, in general, hardly detectable in body fluids and no glycolipid sulfotransferase activity has been demonstrated in them. The cerebroside sulfotransferase was solubilized from rat brains [3, 15, 161 and from rat kidney [I I] and its enzymatic properties characterized. As to substrate specificity, the sulfotransferase catalyzed the sulfation not only of GalCer but also of LacCer [15] and galactosyldiacylglycerol[17]. Recently, Tennekoon et al. [18] highly purified the sulfotransferase from rat kidney; they demonstrated the presence of lipids bound to the enzyme, consisting of cholesterol and phospholipid, which irreversibly affected the enzyme activity. The sulfotransferase activity of partially delipidated microsomes from mouse brain was modulated by the microsomal lipids in an age-dependent manner [7]. These observations suggest that the enzyme activity is modulated by the surrounding lipid. In our previous studies on human cancer tissues, the sulfolipid increased in human lung adenocarcinoma [ 191, gas