The phospholipid-dependence of uridine diphosphate glucuronyltransferase. Temperature-dependence of microsomal enzyme activity (reverse reaction).
Arrhenius plots of the non-latent UDP-glucuronlytransferase reverse reaction (p-nitrophenyl glucuronide donor) activity of guinea-pig microsomal membranes prepared with 15 mM-KCl were linear from 5 to 40 degrees C. These plots for other preparations from guinea-pig and rat liver (i.e. preparations that show transferase latency) exhibited two linear regions intersecting at a transition point near 19--21 degrees C. This discontinuity was abolished when latency was removed by treating the membranes with perturbants of phospholipid-bilayer structure. Thus the temperature-depdendnces of the reverse reaction catalysed by the enzymes of these various preparations are similar to those of the corresponding forward reactions [Pechey, Graham & Wood (1978) Biochem. J. 175, 115--1124]. Perturbants activated the enzyme of KCl-prepared guinea-pig microsomal membranes only slightly and caused no significant alteration to Arrhenius plots of its forward or reverse reaction activities. These results support the 'compartmentation' theory of UDP-glucuronyltransferase lactency.
D000818:Animals; D014453:Glucuronosyltransferase / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000187:drug effects / Q000201:enzymology; D007700:Kinetics; D008041:Linoleic Acids / Q000494:pharmacology; D008244:Lysophosphatidylcholines / Q000494:pharmacology; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D010741:Phospholipases A / Q000494:pharmacology; D010743:Phospholipids / Q000494:pharmacology*; D011092:Polyethylene Glycols / Q000494:pharmacology; D051381:Rats; D013696:Temperature
D008041:Linoleic Acids; D008244:Lysophosphatidylcholines; D010743:Phospholipids; D011092:Polyethylene Glycols; D014453:Glucuronosyltransferase; D010741:Phospholipases A