title: The effect of a temperature-induced phase change within membrane lipids on the regulatory properties of microsomal uridine diphosphate glucuronyltransferase.
abstract: UDP-glucose, UDP-mannose, and UDP-xylose inhibit microsomal UDP-glucuronyltransferase in assays at 6 degrees. None of these compounds affects activity in assays at 37 degrees. Studies with UDP-glucose revealed an abrupt temperature-dependent change in the effect of this compound on the activity of UDP-glucuronyltransferase. Inhibition by UDP-glucose was observed only at temperatures below 16 degrees. UDP-glucose had no effect on activity in assays at temperatures of 16 degrees and above. UDP-N-acetylglucosamine activates UDP-glucuronyltransferase at temperatures at or above 16 degrees, but has no effect on activity below 16 degrees. The lipid portion of the microsomal membrane is known to undergo a phase change at 16 degrees. These data indicate, therefore, that significant alterations in the regulatory properties of UDP-glucuronyltransferase are associated with temperature-induced phase separations within the lipid portion of the microsomal membrane.
mesh_terms: D000818:Animals; D005947:Glucose / Q000494:pharmacology; D014453:Glucuronosyltransferase / Q000037:antagonists & inhibitors*; D006168:Guinea Pigs; D006602:Hexosyltransferases / Q000037:antagonists & inhibitors*; D066298:In Vitro Techniques; D007700:Kinetics; D050356:Lipid Metabolism; D008358:Mannose / Q000494:pharmacology; D008566:Membranes / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D013696:Temperature; D014539:Uridine Diphosphate Sugars / Q000494:pharmacology; D014994:Xylose / Q000494:pharmacology
chemical_list: D014539:Uridine Diphosphate Sugars; D014994:Xylose; D006602:Hexosyltransferases; D014453:Glucuronosyltransferase; D005947:Glucose; D008358:Mannose