Substrates and products of purified rat liver bilirubin UDP-glucuronosyltransferase

N. R. Chowdhury, I. M. Arias, M. Lederstein, Jayanta Roy-Chowdhury

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

To determine whether the isoform of UDP-glucuronosyltransferase which catalyzes the formation of bilirubin monoglucuronide also mediates the formation of bilirubin diglucuronide and other specific sugar conjugates of bilirubin, Wistar rats were treated with clofibrate (300 mg per kg i.p. x 7 days); this resulted in a 200% increase in hepatic transferase specific activity for bilirubin. Proteins from hepatic microsomal fractions were solubilized, and the transferase isoform with activity toward bilirubin was purified by a combination of chromatofocusing, affinity chromatography and hydrophobic chromatography, to apparent homogeneity as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified isoform catalyzed the formation of monoglucuronide and diglucuronide (with UDP-glucoronic acid as a cosubstrate), and glucoside and xyloside (with UDP-glucose and UDP-xylose as respective cosubstrates) of bilirubin and glucuronidation of the carcinogen metabolite 4'-hydroxydimethylaminoazobenzene. It also catalyzed the conversion of bilirubin monoglucuronide to diglucuronide (with UDP-glucuronic acid as cosubstrate, pH optimum 7.8), to mixed glucuronide-glucoside conjugate (with UDP-glucose as a cosubstrate) and to unconjugated bilirubin (with UDP as a cosubstrate, pH optimum 5.5). Each transferase activity was copurified at each purification step. Results of enzyme kinetic studies suggest that UDP-glucuronic acid, UDP-glucose and UDP-xylose recognize a common site. Transferase activities toward bilirubin were not detectable in homozygous Gunn rats liver microsomal fractions; in heterozygous Gunn rats, these activities were reduced by 40 to 60%. The results suggest that conjugation of bilirubin with glucuronic acid, glucose or xylose is catalyzed by a single transferase isoform.

Original languageEnglish (US)
Pages (from-to)123-128
Number of pages6
JournalHepatology
Volume6
Issue number1
StatePublished - 1986

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bilirubin glucuronoside glucuronosyltransferase
Bilirubin
Transferases
Uridine Diphosphate Glucose
Liver
Uridine Diphosphate Xylose
Protein Isoforms
Gunn Rats
Uridine Diphosphate Glucuronic Acid
Uridine Diphosphate
Glucosides
Clofibrate
Glucuronosyltransferase
Glucuronic Acid
Glucuronides
Affinity Chromatography
Sodium Dodecyl Sulfate
Carcinogens
Chromatography
Wistar Rats

ASJC Scopus subject areas

  • Hepatology

Cite this

Substrates and products of purified rat liver bilirubin UDP-glucuronosyltransferase. / Chowdhury, N. R.; Arias, I. M.; Lederstein, M.; Roy-Chowdhury, Jayanta.

In: Hepatology, Vol. 6, No. 1, 1986, p. 123-128.

Research output: Contribution to journalArticle

Chowdhury, NR, Arias, IM, Lederstein, M & Roy-Chowdhury, J 1986, 'Substrates and products of purified rat liver bilirubin UDP-glucuronosyltransferase', Hepatology, vol. 6, no. 1, pp. 123-128.
Chowdhury, N. R. ; Arias, I. M. ; Lederstein, M. ; Roy-Chowdhury, Jayanta. / Substrates and products of purified rat liver bilirubin UDP-glucuronosyltransferase. In: Hepatology. 1986 ; Vol. 6, No. 1. pp. 123-128.
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