N-ACETYLGLUCOSAMINYLTRANSFERASE FROM ASCARIS-SUUM

The occurrence of N-acetylglucosaminyltransferase, the initial step in the synthesis of the carbohydrate moiety of N-linked glycoproteins, is demonstrated in the microsomal fraction of the nematode Ascaris suum. Phosphatidylglycerol stimulated enzyme activity three- to six-fold without affecting the K(m) values of either substrates, uridinediphospho-N-acetylglucosamine or dolichylphosphate. The K(m) values were determined to be about 12-mu-M and 100-mu-g ml-1, respectively. The enzyme activity was strongly inhibited by tunicamycin acting as a competitive inhibitor with respect to the substrate uridinediphospho-N-glucosamine.