title: Inhibition of glycosyltransferases by bis-(p-nitrophenyl)phosphate: general effect and relation to their membrane integration.
abstract: The effect of bis-(p-nitrophenyl)phosphate on various glycosyltransferases involved in protein glycosylation (sialyl-, fucosyl-, galactosyl-, mannosyl- and glucosyltransferases) have been studied using crude enzyme preparations solubilized from rat spleen lymphocytes. Bis-(p-nitrophenyl)phosphate appears as a common inhibitor for every glycosyltransferase reaction utilizing sugar nucleotides as direct donors. In most cases 10 mM inhibitor is sufficient to obtain a 90 per cent inhibition. Kinetic studies achieved with a purified galactosyltransferase preparation reveal that bis-(p-nitrophenyl)phosphate exerts a competitive inhibition towards UDP-galactose binding. Concerning membrane-bound enzymes, the interaction of bis-(p-nitrophenyl)phosphate depends on its accessibility to the enzyme active site. This is shown by the different effect obtained with two UDP-Glc utilizing membrane-bound enzymes : UDP-Glc : phospho-dolichyl glucosyltransferase and UDP-Glc : ceramide glucosyltransferase : the first one not being affected but the second one being markedly inhibited under the same condition, although both are inhibited when the membrane environment is disturbed by detergent. Bis-(p-nitrophenyl)phosphate appears to be a tool to study membrane topology of glycosyltransferases.
mesh_terms: D000818:Animals; D005647:Fucosyltransferases / Q000378:metabolism; D005964:Glucosyltransferases / Q000037:antagonists & inhibitors; D006602:Hexosyltransferases / Q000037:antagonists & inhibitors*; D007700:Kinetics; D008214:Lymphocytes / Q000201:enzymology*; D008364:Mannosyltransferases / Q000037:antagonists & inhibitors; D009596:Nitrophenols / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012799:Sialyltransferases / Q000037:antagonists & inhibitors*; D013154:Spleen / Q000201:enzymology; D014166:Transferases / Q000037:antagonists & inhibitors*
chemical_list: D009596:Nitrophenols; C002887:bis(4-nitrophenyl)phosphate; D014166:Transferases; D005647:Fucosyltransferases; D005964:Glucosyltransferases; D006602:Hexosyltransferases; D008364:Mannosyltransferases; D012799:Sialyltransferases