UDP-N-ACETYL-5-THIO-GALACTOSAMINE IS A SUBSTRATE OF LACTOSE SYNTHASE

Uridine 5'-(N-acetyl-5-thio-galactosaminyl diphosphate) (UDP-5SGalNAc) was synthesized from an N-acetylgalactosamine derivative via ring ope ning-recyclization approach. UDP-5SGalNAc was active as a donor substr ate for lactose synthase, the complex of galactosyltransferase and lac talbumin, giving the disaccharide mimic (5SGalNAc beta[1-->4]GlcNAc) w hich has a sulfur in the ring of the non-reducing sugar. The initial r ate of the formation of the disaccharide mimic was 0.23% that for the natural disaccharide (GalNAc beta[1-->4]GlcNAc). (C) 1997 Elsevier Sci ence Ltd.