Human Blood Group Glycosyltransferases

An N-acetylgalactosaminyltransferase, which converts blood group 0 red blood cells to A cells, was purified to homogeneity from plasma of blood group A, subjects. The enzyme was adsorbed on Sepharose QB, and after washing out the impurities, the enzyme was eluted with UDP. This procedure resulted in a 70,000to lOO,OOO-fold increase in specific activity with recovery of about 80%. Further purification of the enzyme was achieved by Bio-Gel P treatment. The final enzyme preparation showed a single protein band, which coincided with enzyme activity, on acrylamide gel electrophoresis, and revealed a single protein band on sodium dodecyl sulfate-gel electrophoresis. Judging from the molecular weight (90,000 to lOO,OOO), which was estimated by Sephadex gel filtration, and the subunit size estimated by sodium dodecyl sulfate-gel electrophoresis, the enzyme is presumably in a dimeric form. The enzyme required Mn”+ and had optimum activity at pH 6.5 to 7.0.