ACCEPTOR-SUBSTRATE RECOGNITION BY N-ACETYL-GLUCOSAMINYLTRANSFERASE-V - ROLE OF THE MANNOSE RESIDUE IN BETA-DGLCNAC(1-]2)ALPHA-DMAN(1-]6)BETA-DGLCOR

beta BlcNAc(1-->2)alpha Man(1-->6)beta Blc-O(CH2)(7)CH2 (4) is an acce ptor specific for N-acetylglucosaminyltransferase-V (GlcNAcT-V), a bra nching enzyme controlling the biosynthesis of cell-surface Asn-linked oligosaccharides. Three analogs of 4, where the central mannose residu e has been O-methylated at O-3, at O-6, and where the 6-OH group was r eplaced by fluorine, were chemically synthesized, characterized by NMR -spectroscopy and kinetically evaluated as substrates for GlcNAcT-V. A long with results obtained using previously described derivatives of 4 , the conclusion is drawn that none of the OH groups on the Man residu e are critical for recognition by the enzyme. These results should sim plify the design of inhibitors for this important tumor-associated enz yme.