MULTIPLE FORMS AND A DEFICIENCY OF URIDINE DIPHOSPHATE-GLUCURONOSYLTRANSFERASES IN WISTAR RATS

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Uridine diphosphate (UDP)-glucuronosyltransferase (GT) active on androsterone (AD) and 4-nitrophenol (NP) was solubilized from male rat liver microsomes of the Wistar strain. The precipitate obtained in the 60%-satd. ammonium sulfate was purified by diethylaminoethyl (DEAE)-cellulose chromatography and affinity chromatography on UDP-hexanolamine Sepharose 4B. DEAE-cellulose chromatography showed the existence of two peaks of GT active on AD and NP. Peak I was found in rats with the high-activity and low-activity phenotypes in terms of AD glucuronidation and had high NP-GT and low AD-GT activities. In contrast, peak II was found only in rats with the high-activity phenotype, corresponded to high AD-GT activity and had comparatively low NP-GT activities. The corresponding peak in rats with the low-activity phenotype had only NP-GT activity. Comparison of K_m values for AD obtained from microsomes and purified enzymes provides evidence that AD-GT isoenzyme should be deficient in Wistar rats with the low-activity phenotype and that AD glucuronidation should be catalyzed poorly by other GT isoenzyme in these rats.