Bilirubin mono- and diglucuronide formation by human liver in vitro: Assay by high pressure liquid chromatography

Jayanta Roy-Chowdhury, N. R. Chowdhury, G. Wu, R. Shouval, I. M. Arias

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Abstract

Bilirubin diglucuronide, the major pigment in human bile is formed in two steps. Bilirubin is converted to bilirubin monoglucuronide by transfer of the glucuronosyl moiety of uridine diphosphoglucuronic acid catalyzed by the microsomal enzyme, uridine diphosphoglucuronate glucuronosyl transferase (UDP glucuronyl transferase, EC 2.4.1.17). Bilirubin monoglucuronide is converted to bilirubin diglucuronide in vitro by two enzymatic mechanisms: (a) UDP glucuronyl transferase-mediated transfer of a second mole of glucuronic acid from UDP-glucuronic acid to bilirubin monoglucuronide; (b) dismutation of 2 moles of bilirubin monoglucuronide to 1 mole of bilirubin diglucuronide and 1 mole of unconjugated bilirubin, catalyzed by bilirubin monoglucuronide dismutase (bilirubin glucuronoside glucuronosyl transferase EC 2.4.1.95). Assay methods for the three enzymatic mechanisms in human liver homogenate by high pressure liquid chromatography analysis of underivatized bilirubin tetrapyrroles have been developed. UDP glucuronyl transferase was activated in five human liver homogenates with digitonin, Triton X-100 or UDP-N-acetylglucosamine. Greatest activation was observed with Triton X-100. The pH optimum for conversion of bilirubin to bilirubin monoglucuronide was 7.4, and UDP glucuronyl transferase activity was 625 ± 51 nmoles per 20 min per gm liver. At high initial bilirubin concentrations (342 μM), the product of UDP glucuronyl transferase assay with bilirubin as substrate was predominantly bilirubin monoglucuronide. At lower initial bilirubin concentrations (6.5 to 34 μM), up to 15% bilirubin diglucuronide was formed. Glucuronyl transferase-mediated UDP glucuronic acid-dependent conversion of bilirubin monoglucuronide to diglucuronide was assayed using UDP 14C-glucuronic acid. The pH optimum was 7.4, and the rate was 21 ± 7 nmoles per gm liver per 20 min. The rate of bilirubin diglucuronide formation by enzymatic dismutation of bilirubin monoglucuronide was 470 ± 112 nmoles per gm liver per min. The pH optimum ws 6.6. The products of enzymatic dismutation were of the IXα configuration.

Original languageEnglish (US)
Pages (from-to)622-627
Number of pages6
JournalHepatology
Volume1
Issue number6
StatePublished - 1981

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Bilirubin
High Pressure Liquid Chromatography
Glucuronosyltransferase
Uridine Diphosphate Glucuronic Acid
Liver
Transferases
bilirubin glucuronoside glucuronosyltransferase
Octoxynol
Tetrapyrroles
Uridine Diphosphate N-Acetylglucosamine
bilirubin glucuronate
In Vitro Techniques
bilirubin diglucuronide
Digitonin
Glucuronic Acid
Uridine
Bile
Enzymes

ASJC Scopus subject areas

  • Hepatology

Cite this

Bilirubin mono- and diglucuronide formation by human liver in vitro : Assay by high pressure liquid chromatography. / Roy-Chowdhury, Jayanta; Chowdhury, N. R.; Wu, G.; Shouval, R.; Arias, I. M.

In: Hepatology, Vol. 1, No. 6, 1981, p. 622-627.

Research output: Contribution to journalArticle

Roy-Chowdhury, Jayanta ; Chowdhury, N. R. ; Wu, G. ; Shouval, R. ; Arias, I. M. / Bilirubin mono- and diglucuronide formation by human liver in vitro : Assay by high pressure liquid chromatography. In: Hepatology. 1981 ; Vol. 1, No. 6. pp. 622-627.
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abstract = "Bilirubin diglucuronide, the major pigment in human bile is formed in two steps. Bilirubin is converted to bilirubin monoglucuronide by transfer of the glucuronosyl moiety of uridine diphosphoglucuronic acid catalyzed by the microsomal enzyme, uridine diphosphoglucuronate glucuronosyl transferase (UDP glucuronyl transferase, EC 2.4.1.17). Bilirubin monoglucuronide is converted to bilirubin diglucuronide in vitro by two enzymatic mechanisms: (a) UDP glucuronyl transferase-mediated transfer of a second mole of glucuronic acid from UDP-glucuronic acid to bilirubin monoglucuronide; (b) dismutation of 2 moles of bilirubin monoglucuronide to 1 mole of bilirubin diglucuronide and 1 mole of unconjugated bilirubin, catalyzed by bilirubin monoglucuronide dismutase (bilirubin glucuronoside glucuronosyl transferase EC 2.4.1.95). Assay methods for the three enzymatic mechanisms in human liver homogenate by high pressure liquid chromatography analysis of underivatized bilirubin tetrapyrroles have been developed. UDP glucuronyl transferase was activated in five human liver homogenates with digitonin, Triton X-100 or UDP-N-acetylglucosamine. Greatest activation was observed with Triton X-100. The pH optimum for conversion of bilirubin to bilirubin monoglucuronide was 7.4, and UDP glucuronyl transferase activity was 625 ± 51 nmoles per 20 min per gm liver. At high initial bilirubin concentrations (342 μM), the product of UDP glucuronyl transferase assay with bilirubin as substrate was predominantly bilirubin monoglucuronide. At lower initial bilirubin concentrations (6.5 to 34 μM), up to 15{\%} bilirubin diglucuronide was formed. Glucuronyl transferase-mediated UDP glucuronic acid-dependent conversion of bilirubin monoglucuronide to diglucuronide was assayed using UDP 14C-glucuronic acid. The pH optimum was 7.4, and the rate was 21 ± 7 nmoles per gm liver per 20 min. The rate of bilirubin diglucuronide formation by enzymatic dismutation of bilirubin monoglucuronide was 470 ± 112 nmoles per gm liver per min. The pH optimum ws 6.6. The products of enzymatic dismutation were of the IXα configuration.",
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AU - Shouval, R.

AU - Arias, I. M.

PY - 1981

Y1 - 1981

N2 - Bilirubin diglucuronide, the major pigment in human bile is formed in two steps. Bilirubin is converted to bilirubin monoglucuronide by transfer of the glucuronosyl moiety of uridine diphosphoglucuronic acid catalyzed by the microsomal enzyme, uridine diphosphoglucuronate glucuronosyl transferase (UDP glucuronyl transferase, EC 2.4.1.17). Bilirubin monoglucuronide is converted to bilirubin diglucuronide in vitro by two enzymatic mechanisms: (a) UDP glucuronyl transferase-mediated transfer of a second mole of glucuronic acid from UDP-glucuronic acid to bilirubin monoglucuronide; (b) dismutation of 2 moles of bilirubin monoglucuronide to 1 mole of bilirubin diglucuronide and 1 mole of unconjugated bilirubin, catalyzed by bilirubin monoglucuronide dismutase (bilirubin glucuronoside glucuronosyl transferase EC 2.4.1.95). Assay methods for the three enzymatic mechanisms in human liver homogenate by high pressure liquid chromatography analysis of underivatized bilirubin tetrapyrroles have been developed. UDP glucuronyl transferase was activated in five human liver homogenates with digitonin, Triton X-100 or UDP-N-acetylglucosamine. Greatest activation was observed with Triton X-100. The pH optimum for conversion of bilirubin to bilirubin monoglucuronide was 7.4, and UDP glucuronyl transferase activity was 625 ± 51 nmoles per 20 min per gm liver. At high initial bilirubin concentrations (342 μM), the product of UDP glucuronyl transferase assay with bilirubin as substrate was predominantly bilirubin monoglucuronide. At lower initial bilirubin concentrations (6.5 to 34 μM), up to 15% bilirubin diglucuronide was formed. Glucuronyl transferase-mediated UDP glucuronic acid-dependent conversion of bilirubin monoglucuronide to diglucuronide was assayed using UDP 14C-glucuronic acid. The pH optimum was 7.4, and the rate was 21 ± 7 nmoles per gm liver per 20 min. The rate of bilirubin diglucuronide formation by enzymatic dismutation of bilirubin monoglucuronide was 470 ± 112 nmoles per gm liver per min. The pH optimum ws 6.6. The products of enzymatic dismutation were of the IXα configuration.

AB - Bilirubin diglucuronide, the major pigment in human bile is formed in two steps. Bilirubin is converted to bilirubin monoglucuronide by transfer of the glucuronosyl moiety of uridine diphosphoglucuronic acid catalyzed by the microsomal enzyme, uridine diphosphoglucuronate glucuronosyl transferase (UDP glucuronyl transferase, EC 2.4.1.17). Bilirubin monoglucuronide is converted to bilirubin diglucuronide in vitro by two enzymatic mechanisms: (a) UDP glucuronyl transferase-mediated transfer of a second mole of glucuronic acid from UDP-glucuronic acid to bilirubin monoglucuronide; (b) dismutation of 2 moles of bilirubin monoglucuronide to 1 mole of bilirubin diglucuronide and 1 mole of unconjugated bilirubin, catalyzed by bilirubin monoglucuronide dismutase (bilirubin glucuronoside glucuronosyl transferase EC 2.4.1.95). Assay methods for the three enzymatic mechanisms in human liver homogenate by high pressure liquid chromatography analysis of underivatized bilirubin tetrapyrroles have been developed. UDP glucuronyl transferase was activated in five human liver homogenates with digitonin, Triton X-100 or UDP-N-acetylglucosamine. Greatest activation was observed with Triton X-100. The pH optimum for conversion of bilirubin to bilirubin monoglucuronide was 7.4, and UDP glucuronyl transferase activity was 625 ± 51 nmoles per 20 min per gm liver. At high initial bilirubin concentrations (342 μM), the product of UDP glucuronyl transferase assay with bilirubin as substrate was predominantly bilirubin monoglucuronide. At lower initial bilirubin concentrations (6.5 to 34 μM), up to 15% bilirubin diglucuronide was formed. Glucuronyl transferase-mediated UDP glucuronic acid-dependent conversion of bilirubin monoglucuronide to diglucuronide was assayed using UDP 14C-glucuronic acid. The pH optimum was 7.4, and the rate was 21 ± 7 nmoles per gm liver per 20 min. The rate of bilirubin diglucuronide formation by enzymatic dismutation of bilirubin monoglucuronide was 470 ± 112 nmoles per gm liver per min. The pH optimum ws 6.6. The products of enzymatic dismutation were of the IXα configuration.

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