Bilirubin mono- and di-glucuronide formation by purified rat liver microsomal bilirubin UDP-glucuronyltransferase.
Highly purified bilirubin UDP-glucuronyltransferase from Wistar-rat liver, when reconstituted with Gunn-rat liver microsomes (microsomal fraction), was able to catalyse the conversion of unesterified bilirubin into both bilirubin monoglucuronide and diglucuronide. Under zero-order kinetic conditions for monoglucuronide formation, the fraction of bilirubin diglucuronide formed by incubation of bilirubin with the reconstituted highly purified transferase accounted for 18% of total bilirubin glucuronides, which was only slightly lower than the fraction of diglucuronides (23% of total bilirubin glucuronides) formed by incubation with hepatic microsomes in the presence of UDP-N-acetylglucosamine or Lubrol. The reconstituted purified enzyme also catalysed the UDP-glucuronic acid-dependent conversion of bilirubin monoglucuronide into diglucuronide and, when bilirubin was incubated with UDP-glucose or UDP-xylose, the formation of bilirubin glucosides and xylosides respectively. These results suggest that a single microsomal bilirubin UDP-glycosyltransferase may be responsible for the formation of bilirubin mono- and di-glycosides.
D000818:Animals; D001663:Bilirubin / Q000031:analogs & derivatives* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004951:Esterification; D005947:Glucose / Q000378:metabolism; D014453:Glucuronosyltransferase; D006602:Hexosyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D014539:Uridine Diphosphate Sugars / Q000378:metabolism; D014994:Xylose / Q000378:metabolism
D014539:Uridine Diphosphate Sugars; C019787:bilirubin glucuronoside glucuronosyltransferase; C019270:bilirubin diglucuronide; C016266:bilirubin glucuronate; D014994:Xylose; D006602:Hexosyltransferases; D014453:Glucuronosyltransferase; D005947:Glucose; D001663:Bilirubin