Glycosyltransferases in human blood

Abstract

A B S T R A C T Human serum and hemoglobin-free erythrocyte membranes were found to contain a galactosyltransferase which catalyzes the transfer of galactose from UDP-galactose to specific large and small molecular weight acceptors. The requirements for enzyme activity were found to be similar for the enzymes from both sources. However, the membrane-bound enzyme depended on a detergent for maximal activity. Mn++ was an absolute requirement for transfer and uridine nucleoside phosphates were inhibitors. The most effective acceptor for galactose was a glycoprotein containing N-acetylglucosamine residues in the terminal position of its oligosaccharide side chains. N-acetylglucosamine was also an acceptor. While the presence of a-lactalbumin in the incubation medium resulted in a significant decrease in the transfer of galactose to N-acetylglucosaxmine, glucose, which was not an acceptor for galactose in the absence of a-lactalbumin, became an excellent acceptor. The serum enzyme catalyzed the transfer of 54 nmoles of galactose per milliliter of serum per hour and its apparent Km for UDP-galactose was 7.5 X 10'M. The membrane enzyme had a similar apparent Km. Using a quantitative assay system the enzyme was found to be present in all individuals studied, regardless of their blood type, secretor status, or sex.

Cancer-associated isoenzyme of serum galactosyltransferase.

“…A significant portion of serum proteins are glycoproteins and the biosynthesis of ABO blood group substances also requires sugar additions through the action of glycosyltransferases (12). Although some glycosyltransferases appear to be membrane-associated enzymes when prepared from tissue homogenates, these transferases have also been detected as soluble enzymes in various body fluids, including rat and human serum (6,7).…”

“…Kessel and Allen reported elevated sialyltransferase activity in the plasma of cancer patients (5). 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 occurrence of a β‐galactosyltransferase in normal human urine

“…[12],andserum [13]; bovine milk [14][15][16][17] ; bovine and guinea pig mammary gland [ 181; porcine serum and liver [ 191 and a variety of other sources [20].…”

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

“…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].…”