Cytochrome P450 enzymes are responsible for the metabolism of most commonly used drugs. Among these enzymes, CYP3A forms mediate the clearance of around 40-50% of drugs and may also play roles in the biotransformation of endogenous compounds. CYP3A forms are expressed both in the liver and extrahepatically. However, little is known about the expression of CYP3A proteins in specific regions of t...

CYP3A4, the most abundant form of cytochrome P450 in the human adult liver, shows wide interindividual variation in its activity. This variability is thought to be caused largely by transcriptional and genetic factors, yet the underlying mechanisms are poorly understood. The purpose of this study was to clarify the mechanisms controlling the CYP3A4 gene transcription and to search for genetic p...

A systematic in vitro study was carried out to elucidate the enzymes responsible for the metabolism of haloperidol (HAL) using human liver microsomes and recombinant human cytochrome P450 isoenzymes. In the first series of experiments, recombinant cytochrome P450 (P450) isoenzymes were used to evaluate their catalytic involvement in the metabolic pathways of HAL. Recombinant CYP3A4, CYP3A5, and...

Recent data suggest that the role of CYP3A4 in imatinib metabolism is smaller than presumed. This study aimed to evaluate the quantitative importance of different cytochrome P450 (P450) enzymes in imatinib pharmacokinetics. First, the metabolism of imatinib was investigated using recombinant P450 enzymes and human liver microsomes with P450 isoform-selective inhibitors. Thereafter, an in silico...

In the world and Vietnam, a great number of toxic substances from industrial agricultural activities, food production, healthcare services are daily released into environment. Many exogenous harmful procarcinogens, but become carcinogens by bioactivation human cytochrome P450 enzymes (CYPs). Thus, development analytical testing for rapid detection procarcinogens plays crucial role in safety env...

Previous case-only studies have shown that men with the CYP3A4*1B promoter variant are at an increased risk of developing more aggressive forms of prostate cancer. However, no changes in CYP3A4 activity have been found in CYP3A4*1B carriers, suggesting that its association with disease may simply reflect linkage disequilibrium with another functional variant. CYP3A5 is located within 200 kb of ...

CYP3A4 and CYP3A5 exhibit significant overlap in substrate specificity but can differ in product regioselectivity and formation activity. To further explore this issue, we compared the kinetics of product formation for eight different substrates, using heterologously expressed CYP3A4 and CYP3A5 and phenotyped human liver microsomes. Both enzymes displayed allosteric behavior toward six of the s...

Grapefruit juice has been found to cause an increase in the oral bioavailability of many therapeutic agents. Such interactions are believed to result from the mechanism-based inhibition of CYP3A4 activity in the intestine. Furanocoumarin dimers present in the juice have been found to be extremely potent inhibitors of CYP3A4 activity. The aim of this work was to synthesize and test a series of d...

The objectives of this study were to characterize and compare the reversible inhibition and time-dependent inactivation of cytochromes P450 3A4 and 3A5 (CYP3A4 and CYP3A5) by erythromycin, diltiazem, and nicardipine. In the following experiments, we used cDNA-expressed CYP3A Supersomes and CYP3A-phenotyped human liver microsomes. We estimated the apparent constants for reversible inhibition (Ki...

Drug efflux by intestinal P-glycoprotein (P-gp) is known to decrease the oral bioavailability of many CYP3A4 substrates. We hypothesized that the interplay occurring between P-gp and CYP3A4 at the apical membrane would increase the opportunity for drug metabolism. To define the roles of P-glycoprotein (P-gp) and CYP3A4 in controlling the extent of intestinal absorption and metabolism, two subst...