Substrate specificity and properties of uridine diphosphate glucuronyltransferase purified to apparent homogeneity from phenobarbital-treated rat liver.

1. The purification to homogeneity of stable highly active preparations of UDP-glucuronyltransferase from liver of phenobarbital-treated rats is briefly described. 2. A single polypeptide was visible after sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, of mol.wt.57000. 3. Antiserum raised against the pure enzyme produces a single sharp precipitin line after Ouchterlony double-diffusion analysis. 4. The pure UDP-glucuronyltransferase isolated from livers of untreated and phenobarbital-pretreated rats appears to be the same enzyme. 5. The Km (UDP-glucuronic acid) of the pure enzyme is 5.4 mM. 6. The activity of the pure enzyme towards 2-aminophenol can still be activated 2-3-fold by diethylnitrosamine. 7. UDP-glucose and UDP-galacturonic acid are not substrates for the purified enzyme. 8. The final preparation catalysed the glucuronidation of 4-nitrophenol, 1-naphthol, 2-aminophenol, morphine and 2-aminobenzoate. 9. Activities towards 4-nitrophenol, 1-naphthol and 2-aminophenol were all copurified. The proposed heterogeneity of UDP-glucuronyltransferase is discussed.