Catechol estrogens are major estrogen metabolites in mammals and are the most potent naturally occurring inhibitors of catecholamine metabolism. These estrogen compounds have been implicated in carcinogenic activity and the 4/2-hydroxyestradiol concentration has been shown to be elevated in neoplastic human mammary tissue compared to normal human breast tissue. Three human liver UDP-glucuronosy...

Serotonin is a specific in vitro substrate for human UDP-glucuronosyltransferase (UGT) 1A6. In this study, the contribution of UGT1A6 to the glucuronidation of endogenous structural analogs of serotonin, including 5-hydroxytryptophol, N-acetylserotonin, and 6-hydroxymelatonin, was evaluated using available recombinant human UGT isoforms, human liver microsomes, and liver microsomes from animals...

The nicotine and cotinine N-glucuronidations in human liver microsomes were characterized. The Eadie-Hofstee plots of nicotine N-glucuronidation in human liver microsomes were clearly biphasic, indicating the involvement of multiple enzymes. The apparent K(m) and V(max) values were 33.1 +/- 28.1 micro M and 60.0 +/- 21.0 pmol/min/mg and 284.7 +/- 122.0 micro M and 124.0 +/- 44.0 pmol/min/mg for...

Epirubicin is one of the most active agents for breast cancer. The formation of epirubicin glucuronide by liver UDP-glucuronosyltransferase (UGT) is its main inactivating pathway. This study aimed to investigate epirubicin glucuronidation in human liver microsomes, to identify the specific UGT isoform for this reaction, and to correlate epirubicin glucuronidation with other UGT substrates. Micr...

Acetaminophen is cleared primarily by hepatic glucuronidation. Polymorphisms in genes encoding the acetaminophen UDPglucuronosyltransferase (UGT) enzymes could explain interindividual variability in acetaminophen glucuronidation and variable risk for liver injury after acetaminophen overdose. In this study, human liver bank samples were phenotyped for acetaminophen glucuronidation activity and ...

The metabolism of 3-([3-(2-Chlorophenyl)-4,5-dihydro-5-thioxo-1H-1,2,4-triazol-1-yl]methyl)benzonitrile (AR-C133611XX) was studied in isolated dog hepatocytes. The major metabolite of AR-C133611XX was characterized by high performance liquid chromatography-mass spectrometry and NMR and found to be the product of direct glucuronidation. Evidence from 1H and 13C-NMR chemical shifts and a long-ran...

Glucuronidation mediated by uridine 5'-diphospho (UDP)-glucuronosyltransferase is an important detoxification pathway. However, identifying a selective probe of UDP- glucuronosyltransferase is complicated because of the significant overlapping substrate specificity displayed by the enzyme. In this paper, desacetylcinobufagin (DACB) 3-O- and 16-O-glucuronidation were found to be isoform-specific...

UDP-glucuronosyltransferases (UGTs) are a family of metabolic enzymes responsible for the detoxification of a wide range of endoand xenobiotics, including drugs. UGTmediated metabolism is a major determinant of the pharmacokinetic behavior of many drugs in the human body, contributing to parameters such as bioavailability and elimination. UGTs catalyze the transfer of glucuronic acid from UDP-g...

Esculetin (6,7-dihydroxycoumarin) and its C-4 derivatives have multiple pharmacologic activities, but the poor metabolic stability of these catechols has severely restricted their application in the clinic. Glucuronidation plays important roles in catechols elimination, although thus far the effects of structural modifications on the metabolic selectivity and the catalytic efficacy of the human...