n-Alkylglucosides Serve as Acceptors for Galactosyltransferases from Rat Liver Golgi Vesicles

Abstract

n-Alkyl α- and β-D-glucopyranosides with different alkyl chain lengths (Glc-O-CxH2x+1) and n-octyl β-D-thioglucopyranoside (Glc-S-C8H17) were synthesized, and used as acceptors for galactosyltransferases from rat liver Golgi vesicles. Only the β-anomers were galactosylated and at constant substrate concentration, the reaction rates reached a maximum for medium alkyl chain lengths (C6C8 and C10). Apparent Kmand Vmax values decreased with increasing alkyl chain length. The reaction products were identified as n-alkyl plactosides by means of thin layer chromatography, fast atom bombardment mass spectrometry and 1H-NMR spectroscopy. Competition experiments showed that UDP-Gal: N-acetylglucosamine β1-4-galactosyltransferase (EC 2.4.1.38) and not UDP-Gal: glucosylceramide β1-4-galactosyltransferase (lacto-sylceramide synthase, GalT-2) was responsible for the galactosylation of alkyl glucosides. © 1995, Walter de Gruyter & Co. All rights reserved.