Studies on the latency of UDP-galactose-asialo-mucin galactosyltransferase activity in microsomal and Golgi subfractions from rat liver.
The activity of UDPgalactose-asialo-mucin galactosyltransferase (EC 2.4.1.74) in microsomal and Golig subfractions was stimulated 2.4-fold after disruption of the membrane permeability barrier by hypotonic incubation. In the presence of Triton X-100, galactose transfer to asialo-mucin was increased 12-fold in rough microsomes and 5-fold in smooth microsomes both with and without hypotonic incubation; while in the Golgi subfractions no stimulation by detergent was observed. These experiments indicate differences in enzyme-lipid or enzyme-protein interactions in microsomes and Golgi membranes. Furthermore, these results strongly support the conclusion that the UDP-galactose-asialo-mucin galactosyltransferase activity in microsomal fractions is not due to contamination by Golgi vesicles but represents an enzyme activity endogenous to the endoplasmic reticulum.
D000818:Animals; D004789:Enzyme Activation; D005700:Galactosyltransferases / Q000378:metabolism*; D006056:Golgi Apparatus / Q000201:enzymology*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D009077:Mucins / Q000378:metabolism*; D017830:Octoxynol; D009994:Osmolar Concentration; D011092:Polyethylene Glycols / Q000494:pharmacology; D051381:Rats; D014531:Uridine Diphosphate Galactose / Q000378:metabolism*; D014539:Uridine Diphosphate Sugars / Q000378:metabolism*
D009077:Mucins; D014539:Uridine Diphosphate Sugars; D014531:Uridine Diphosphate Galactose; D011092:Polyethylene Glycols; D017830:Octoxynol; D005700:Galactosyltransferases