Biochemical and immunologic characterization of galactosyltransferase purified from the ascites of ovarian cancer patients.

Galactosyltransferase appears to be a promising marker for ovarian carcinoma. For an understanding of its role in this cancer, the enzyme was purified from the ascites of ovarian cancer patients, and its biochemical and immunologic properties were studied. For adequate recovery and stability, Triton X-100 (0.01%) was necessary in all the buffers used for the purification of this enzyme. Immunoglobulins were not detectable in this preparation, which showed a single band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Electrophoresis under nondenaturing conditions resolved the enzyme into two to three active components. An antiserum in rabbits, however, produced a single precipitin line suggesting a single determinant. By chromatography in concanavalin A-Sepharose 4B, the enzyme can be resolved into two components (F-1 and F-2). Purified galactosyltransferase and components F-1 and F-2 all catalyzed the transfer of galactose from UDP-galactose to alkali-stable beta-N-glycosidic acceptors, as well as to alkali-labile beta-O-glycosidic mucin-type acceptors. In addition, they catalyzed the N-acetyllactosamine synthetase reaction and, in the presence of alpha-lactalbumin, the lactose synthetase reaction. Galactosyltransferase and components F-1 and F-2 differed in their sensitivity to alpha-lactalbumin-induced inhibition of N-acetyllactosamine synthesis. Galactosyltransferase in the malignant ascites exists as different isoforms, which do not differ significantly in major biochemical and immunologic properties.