Document Detail


Liver microsomal beta-glucuronidase and UDP-glucuronyltransferase.
MedLine Citation:
PMID:  230     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Both UDP-glucuronyltransferase (GT) and beta-glucuronidase (betaG) were assayed in untreated liver microsomes. Optimum assay conditions were established with rat liver microsomes using p-nitrophenol (pNP) and its glucuronide (pNPGA) at the pH optima of GT (7.5) and betaG (4.5). The activities of the two enzymes were compared using microsomes from rats, mice, pigs, cattle and horses, with pNP, pNPGA, and phenolphthalein as substrate, in the presence of various cofactors and inhibitors at pH 7.5 and 4.5. These data disclose pronounced differences with respect to species, substrate and other experimental conditions, thereby precluding the establishment of general optimum conditions. The two enzymes were also assayed under strictly identical conditions using pNP and pNPGA and rat liver microsomes at pH 7.5 in the presence and absence of UDP-glucuronate disodium (UDPGA), activators (ATP;UDP-N-acetylglucosamine) and inhibitors. When provided with a functional level of UDPGA, both enzymes proved active under those conditions, and a conjugation-deconjugation interplay was indicated. The two processes could be selectively and totally inhibited by Zn2+ and saccharolactone. The results suggest that conjugation-deconjugation-reconjugation cycles may be operative in the metabolism of drugs in vivo, taking place already at the level of the liver endoplasmic reticulum.
Authors:
I Schöllhammer; D S Poll; M H Bickel
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Enzyme     Volume:  20     ISSN:  0013-9432     ISO Abbreviation:  Enzyme     Publication Date:  1975  
Date Detail:
Created Date:  1976-02-09     Completed Date:  1976-02-09     Revised Date:  2003-11-14    
Medline Journal Info:
Nlm Unique ID:  1262265     Medline TA:  Enzyme     Country:  SWITZERLAND    
Other Details:
Languages:  eng     Pagination:  269-76     Citation Subset:  IM    
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms
Descriptor/Qualifier:
Adenosine Triphosphate / pharmacology
Animals
Cations, Divalent
Cattle
Glucuronidase / metabolism*
Glucuronosyltransferase / metabolism*
Hexosyltransferases / metabolism*
Horses
Hydrogen-Ion Concentration
Kinetics
Lactones / pharmacology
Male
Mice
Microsomes, Liver / enzymology*
Rats
Species Specificity
Sugar Alcohols / pharmacology
Swine
Uridine Diphosphate N-Acetylglucosamine / pharmacology
Zinc / pharmacology
Chemical
Reg. No./Substance:
0/Cations, Divalent; 0/Lactones; 0/Sugar Alcohols; 528-04-1/Uridine Diphosphate N-Acetylglucosamine; 56-65-5/Adenosine Triphosphate; 7440-66-6/Zinc; EC 2.4.1.-/Hexosyltransferases; EC 2.4.1.17/Glucuronosyltransferase; EC 3.2.1.31/Glucuronidase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


Previous Document:  Ecological observation of the 137Cs-contamination in beef of animals from the southern-Bavarian area...
Next Document:  Biochemical aspects of renal ammonia formation in metabolic acidosis.