Enzymatic basis for the structural changes of asparagine-linked sugar chains of membrane glycoproteins of baby hamster kidney cells induced by polyoma transformation.

K Yamashita,Y Tachibana,T Ohkura,A Kobata

doi:10.1016/s0021-9258(18)89216-x

Abstract

Previous studies indicated that enrichment of the GlcNAc beta 1----6Man alpha 1---- group with concomitant decrease of the GlcNAc beta 1----4Man alpha 1---- group occurs in the complex-type asparagine-linked sugar chains of the membrane glycoproteins of baby hamster kidney cells transformed by polyoma virus. The enzymatic basis of the chemical change is reported in this paper. By using oligosaccharides isolated from the urine of patients with a variety of exoglycosidase deficiencies, beta-N-acetylglucosaminyltransferases in the cell homogenate were successfully assayed separately. Both baby hamster kidney cells and their polyoma transformants contain beta-N-acetylglucosaminyltransferases I, II, IV, V, and VI, but not beta-N-acetylglucosaminyltransferase III. The beta-N-acetylglucosamine residue added by each beta-N-acetylglucosaminyltransferase (GnT) is shown below. (formula see text) Comparative studies of the specific activities of the five beta-N-acetylglucosaminyltransferases in the two cell lines revealed that the value of beta-N-acetylglucosaminyltransferase V in the polyoma transformant was twice of that in the normal cells, while those of the other four transferases in the two cell lines were not significantly different. Therefore the increase in beta-N-acetylglucosaminyltransferase V may be the direct cause of the changes found in the sugar chains of surface glycoproteins in baby hamster kidney cells transformed by polyoma virus.

Highlights

GlcNAc~l-AManal, group with concomitantde- behavior of the glycopeptides obtained frombaby hamster crease of the GlcNAc~l-4Manal+ group occurs in kidney (BHK’) cells and their polyoma transformants (Pythecomplex-typeasparagine-linkedsugarchainsof BHK cells) on a concanavalin A-Sepharose column,we sugthe membrane glycoproteins of baby hamster kidney gested that the increase in size of the sugar chains of glycocells transformedbypolyoma virus
The B-N-acetylglucosamine residuaedded by each B-N-acetylglucosaminyltransferas(eGnT)is shown beand qualitative differencesin plasma membrane glycoproteins of cells [7,8] as well as purified glycoproteins
Several differences have been found in the structures of sugar chains of glycoproteins producedin normal and malignant cells.One of them is a characteristic increase in the molecular weightof the asparagine-linkedsugar chains which has been widely observed in theplasma membrane glycoproteins of transformed and malignant cells from a variety of mammals [1];malignant cells in culture were examinedin

Summary

RESULTS AND DISCUSSION

Several differences have been found in the structures of sugar chains of glycoproteins producedin normal and malignant cells.One of them is a characteristic increase in the molecular weightof the asparagine-linkedsugar chains which has been widely observed in theplasma membrane glycoproteins of transformed and malignant cells from a variety of mammals [1];malignant cells in culture were examinedin. This article must thereforebe hereby marked“advertisement” in accordance with 18 U.S.C.Section 1734 solelyto indicate this fact. The abbreviations used are: BHK, baby hamster kidney; XylNAc, N-acetylxylosaminitol.SubscriptOTisused to indicateNaBaH,reduced oligosaccharides. Subscript OH is used to indicate NaBH,-reduced oligosaccharides. Request Document No “-1621, cite the authors, and include a check or money order for $2.40 perset of photocopies.

GlcNAc Transferases in Transformed Cell

The results indicated that theincrease in concentration of

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