UDP-N-ACETYLGLUCOSAMINE-DOLICHYL-PHOSPHATE N-ACETYLGLUCOSAMINE-1-PHOSPHATE TRANSFERASE IS AMPLIFIED IN TUNICAMYCIN-RESISTANT SOYBEAN CELLS

A tunicamycin-resistant soybean cell line was developed by gradually i ncreasing the concentration of tunicamycin in the growth medium. At th e final stage, the resistant cells could survive in media containing 6 0 mu g/ml of tunicamycin, whereas normal cells show a greatly retarded growth rate at 0.5 mu g/ml of antibiotic. The tunicamycin-resistant c ells had a greater than 40-fold increase in the activity of the enzyme UDP-GlcNAc:dolichyl-P GlcNAc1P transferase, a 2-3-fold increase in th e activity of dolichyl-P-mannose synthase, but no increase in the acti vities of other enzymes of the lipid-linked saccharide pathway such as dolichyl-P-glucose synthase or mannosyl transferases. There was also no change in the activities of the glycoprotein-processing enzymes, gl ucosidase I or glucosidase II, as compared to wild-type cells. The inc rease in GlcNAc1P transferase was due to an increased production of en zyme, as seen by a dramatic increase in the amount of a 39-kDa protein , which is presumed to be this enzyme protein. The GlcNAc1P transferas e from tunicamycin-resistant cells was equally sensitive to tunicamyci n as was the wild-type enzyme, but was considerably more labile to tem peratures above 30 degrees C, The activity in tunicamycin-resistant ce lls was greatly stimulated by exogenous dolichyl-P, The spectrum of ol igosaccharides from labeled lipid-linked oligosaccharides was similar in wild-type and tunicamycin-resistant soybean cells, but the resistan t cells had significantly greater amounts of the shorter and much lowe r amounts of the larger-sized oligosaccharides.