Role of cell membrane galactosyltransferase in concanavalin A agglutination of erythrocytes

Abstract

It has been previously observed that rabbit erythrocyte cell surface galactosyltransferase appears to play a role in concanavalin A agglutination of these erythrocytes (Podolsky et al., 1974). Further, a correlation between the occurrence or level of cell surface galactosyltransferase and concanavalin A agglutinability of other cell types has also been observed. The mechanism by which rabbit erythrocyte galactosyltransferase participates in concanavalin A agglutination has now been further defined. The enzyme was solubilized and purified. Characterization of the enzyme properties has shown them to be similar to those reported for other purified galactosyltransferases. Amino acid and carbohydrate analysis showed a high asparagine content and the presence of D-mannose. Specific alpha-mannosidase treatment of the enzyme showed that some of these D-mannose residues were terminal sugars. The purified enzyme also conferred concanavalin A agglutinability to non-agglutinable human erythrocytes. However, the ability to confer concanavalin A agglutinability was unrelated to the enzyme activity per se (as measured with fetuin acceptor) but appeared to be entirely dependent on the presence of terminal alpha-linked D-mannosyl residues in the enzyme structure. These findings suggest that the presence of terminal alpha-mannosidyl residues on cell surface glycoproteins such as galactosyltransferase may be the determining factor in agglutination of cells by concanavalin A.

Characterization of glycoprotein—galactosyltransferase activity in ascitic fluid of Balb/c‐YC8 mice

“…In preliminary experiments, we have defined some requirements for galactose transfer in YC8 ascitic fluids and sera; the results we obtained are described [6] with normal human and cancerous sera.…”

“…Galactosyltransferase activities have been described in various biological fluids [1][2][3][4][5] and more recently in human cancer sera [6], but to our knowledge not yet in cancerous ascitic fluids. So we have undertaken to investigate the galactosyltransferase activity of ascitic fluids towards endogenous and exogenous acceptors, and comparatively i n sera from the Balb/c mouse strain bearing the ascitic transplantable isogenic tumor YC8, a lymphoma which possesses at least two tumor membrane antigens [7].…”

Cancer-associated isoenzyme of serum galactosyltransferase.

“…Polyacrylamide gel electrophoresis of sera and detection of galactosyltransferase activity from slices of polyacrylamide gels were performed by the method of Podolsky and Weiser (9). It was observed that the cancer-associated cathodal peak of activity (isoenzyme II) could not be detected * To whom reprints should be addressed.…”

“…Galactosyltransferase activity has also been detected in rat and human serum as a soluble activity (6,7), but the total activity was not previously found to be elevated in cancer patients unless liver disease was also present (8). However, by means of discontinuous polyacrylamide gel electrophoresis Podolsky and Weiser were able to detect in cancer patients a slower moving peak of activity that separated well from the major, more anodally directed peak of activity found in all patients (9). The present report describes the cancer patients who were tested for serum galactosyltransferase isoenzymes, compares them with disease and normal controls, and examines possible clinical and laboratory correlations with serum levels of these isoenzymes.…”

“…Galactosyltransferase activity in whole serum was measured as previously described (9). The glycoprotein acceptor used for this enzyme assay was fetuin minus its terminal sialic acid and penultimate galactose residues (10).…”