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The phospholipid-dependence of uridine diphosphate glucuronyltransferase. Temperature-dependence of microsomal enzyme activity (reverse reaction).


ABSTRACT: 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.

SUBMITTER: Cummings J 

PROVIDER: S-EPMC1161381 | biostudies-other | 1980 Feb

REPOSITORIES: biostudies-other

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