Beta-1,4-mannosyl-glycoprotein beta-1,4-N-acetylglucosaminyltransferase III activity in human B and T lymphocyte lines and in tonsillar B and T lymphocytes.
beta-1,4-mannosyl-glycoprotein beta-1,4-N-acetylglucosaminyltransferase III (GlcNAc-T III) catalyzes the incorporation of a "bisecting" N-acetylglucosamine (GlcNAc) residue in beta 1-4 linkage to the beta-linked mannose of the core of asparagine linked-protein bound oligosaccharides (N-glycans). The activity of GlcNAc-T III was determined in Triton X-100 extracts of four human Epstein-Barr virus (EBV)-infected B-cell lines, in four T-cell lines originally established from lymphocytes of patients with acute lymphatic leukemia, and in human tonsillar B and T lymphocytes. The four EBV-transformed B-cell lines showed appreciable GlcNAc-T III activities (ranging from 3.4 to 19.0 nmol.h-1.mg protein-1), while the tonsillar resting B lymphocytes had much less activity (0.68 nmol.h-1.mg protein-1). The four T-cell lines and the tonsillar T lymphocytes had negligible GlcNAc-T III activities (ranging from 0.02 to 0.25 nmol.h-1.mg protein-1). Enzyme product was identified by high resolution proton nuclear magnetic resonance spectroscopy and methylation analysis. This is the first demonstration of GlcNAc-T III activity in human lymphocytes. The presence of GlcNAc-T III in B-cell lines correlates with the reported occurrence of bisecting GlcNAc residues in the oligosaccharides of human immunoglobulins G, A1, M, and D, tonsillar class II antigens, and membrane glycoproteins from B lymphocytes. The negligible GlcNAc-T III activity of the four human T-cell lines and of tonsillar T lymphocytes agrees with the reported absence of bisected structures in N-glycans from human T lymphocyte membrane glycoproteins.
Narasimhan
S
S
Division of Biochemistry Research, Hospital for Sick Children, Toronto, Ont., Canada.
Lee
J W
JW
Cheung
R K
RK
Gelfand
E W
EW
Schachter
H
H
D000117:Acetylglucosamine / Q000378:metabolism; D001216:Asparagine / Q000378:metabolism; D001402:B-Lymphocytes / Q000201:enzymology*; D002461:Cell Line, Transformed; D005964:Glucosyltransferases / Q000378:metabolism*; D004854:Herpesvirus 4, Human; D006801:Humans; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008358:Mannose / Q000378:metabolism; D008745:Methylation; D017351:N-Acetylglucosaminyltransferases; D009844:Oligosaccharides / Q000378:metabolism; D014066:Palatine Tonsil / Q000166:cytology; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000201:enzymology; D013601:T-Lymphocytes / Q000201:enzymology*; D014407:Tumor Cells, Cultured
D009844:Oligosaccharides; D001216:Asparagine; D005964:Glucosyltransferases; D017351:N-Acetylglucosaminyltransferases; C054599:beta-1,4-mannosyl-glycoprotein beta-1,4-N-acetylglucosaminyltransferase; D008358:Mannose; D000117:Acetylglucosamine