Effect of Albumin and Cytosol on Enzyme Kinetics of Tolbutamide Hydroxylation and on Inhibition of CYP2C9 by Gemfibrozil in Human Liver Microsomes

2002 ◽  
Vol 302 (1) ◽  
pp. 43-49 ◽  
Author(s):  
Jun-Sheng Wang ◽  
Xia Wen ◽  
Janne T. Backman ◽  
Pertti J. Neuvonen
Keyword(s):  
Enzyme Kinetics ◽  
Human Liver ◽  
Liver Microsomes ◽  
Human Liver Microsomes ◽  
Kinetics Of

Metabolic Characteristics of SM-1, a Novel PAC-1 Derivative, in Human Liver Microsomes

2021 ◽  
Vol 17 ◽  
Author(s):  
Ya Gong ◽  
Peiqi Wang ◽  
Jianming Li ◽  
Jinsong Ding
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
Enzyme Kinetics ◽  
Human Liver ◽  
Liver Microsomes ◽  
Human Liver Microsomes ◽  
Spectrometry Method ◽  
Mass Spectrometry Method ◽  
Metabolic Characteristics ◽  
Kinetics Of

Background and Objectives: SM-1 is a new synthetic small molecule compound with antitumor activity. The metabolism of SM-1 is a key parameter that needs to be evaluated to provide further insight into drug safety and efficacy in the early phases of drug development. Methods and Results: In this study, the biotransformation process of SM-1 including the metabolic pathways and major metabolites was investigated based on a liquid chromatography-mass spectrometry method. Upon incubation of SM-1 with human liver microsomes, five metabolites were identified, namely dihydrodiol formation (R1), hydroxylation (R2, R3 and R5), and debenzylation (R4) of SM-1, with R1 and R4 being the major metabolites. The enzyme kinetic parameters of SM-1 were determined by a liquid chromatography tandem mass spectrometry method. The enzyme kinetics of SM-1 obeyed the Michaelis-Menten equation. The Vmax, Km, and CLint of SM-1 in HLMs were 14.5 nmol/mg protein/h, 6.32 μM, and 2.29 mL/mg protein/h, respectively. The chemical inhibition studies showed that CYP450 isoenzymes were responsible for SM-1 metabolism in HLMs and CYP3A4 was the major CYP450 isoenzyme involved in the metabolism of SM-1; these findings were confirmed by using the human recombinant CYP3A4. Conclusions : Through identification of the biotransformation pathways and enzyme kinetics of SM-1, the metabolic enzymes for SM-1 in HLMs are characterized.

Effect of Commonly Used Organic Solvents on the Kinetics of Cytochrome P450 2B6- and 2C8-Dependent Activity in Human Liver Microsomes

2007 ◽  
Vol 35 (11) ◽  
pp. 1990-1995 ◽  
Author(s):  
Ragini Vuppugalla ◽  
Shu-Ying Chang ◽  
Hongjian Zhang ◽  
Punit H. Marathe ◽  
David A. Rodrigues
Keyword(s):  
Cytochrome P450 ◽  
Organic Solvents ◽  
Human Liver ◽  
Liver Microsomes ◽  
Human Liver Microsomes ◽  
Cytochrome P450 2B6 ◽  
Dependent Activity ◽  
Kinetics Of

scholarly journals Kinetics of tris (1-chloro-2-propyl) phosphate (TCIPP) metabolism in human liver microsomes and serum

Chemosphere ◽  
2016 ◽  
Vol 144 ◽  
pp. 1299-1305 ◽  
Author(s):  
Nele Van den Eede ◽  
Gregg Tomy ◽  
Fang Tao ◽  
Thor Halldorson ◽  
Stuart Harrad ◽  
...  
Keyword(s):  
Human Liver ◽  
Liver Microsomes ◽  
Human Liver Microsomes ◽  
Kinetics Of

scholarly journals Kinetics of Trihalogenated Acetic Acid Metabolism and Isoform Specificity in Liver Microsomes

2011 ◽  
Vol 30 (5) ◽  
pp. 551-561 ◽  
Author(s):  
Shakil A. Saghir ◽  
Burhan I. Ghanayem ◽  
Irvin R. Schultz
Keyword(s):  
Human Liver ◽  
Liver Microsomes ◽  
Human Liver Microsomes ◽  
Water Disinfection ◽  
Metabolic Clearance ◽  
Interspecies Differences ◽  
P450 Reductase ◽  
Cyp 2E1 ◽  
Chemical Inhibitors ◽  
Kinetics Of

This study determined the metabolism of 3 drinking water disinfection by-products (halogenated acetic acids [HAAs]), bromodichloroacetic acid (BDCAA), chlorodibromoacetic acid (CDBAA), and tribromoacetic acid (TBAA), using rat, mouse, human liver microsomes, and recombinant P450. Metabolism proceeded by reductive debromination forming a di-HAA; the highest under nitrogen >>2% oxygen > atmospheric headspaces. Vmax for the loss of tri-HAA was 4 to 5 times higher under nitrogen than atmospheric headspace. Intrinsic metabolic clearance was TBAA>CDBAA>>BDCAA. At the high substrate concentrations, tri-HAA consumption rate was 2 to 3 times higher than the formation of di-HAA. Liberation of Br− from TBAA corresponded to the expected amount produced after DBAA formation, indicating retention of Br− by additional metabolite/metabolites. Subsequent experiments with CDBAA detected negligible formation of chlorodibromomethane (CDBM) and failed to account for the missing tri-HAA. Carbon monoxide and especially diphenyleneiodonium ([DPI] P450 reductase inhibitor) blocked CDBAA metabolism. Other chemical inhibitors were only partially able to block CDBAA metabolism. Most effective were inhibitors of CYP 2E1 and CYP 3A4. Immunoinhibition studies using human liver microsomes and anti-human CYP 2E1 antibodies were successful in reducing CDBAA metabolism. However, CDBAA metabolism in wild-type (WT) and CYP 2E1 knockout (KO) mouse liver microsomes was similar, suggesting significant interspecies differences in CYP isoform in tri-HAA metabolism. Additional assessment of CYP isoform involvement was complicated by the finding that recombinantly expressed rat and human P450 reductase was able to metabolize CDBAA, which may be a contributing factor in interspecies differences in tri-HAA metabolism.

Cytochrome P-450 2B6 Is Responsible for Interindividual Variability of Propofol Hydroxylation by Human Liver Microsomes

2001 ◽  
Vol 94 (1) ◽  
pp. 110-119 ◽  
Author(s):  
Michael H. Court ◽  
Su X. Duan ◽  
Leah M. Hesse ◽  
Karthik Venkatakrishnan ◽  
David J. Greenblatt
Keyword(s):  
Enzyme Kinetics ◽  
Protein Content ◽  
Human Liver ◽  
Interindividual Variability ◽  
Liver Microsomes ◽  
High Capacity ◽  
Human Liver Microsomes ◽  
High Affinity ◽  
Hepatic Microsomes ◽  
Cytochrome P 450

Background Oxidation of propofol to 4-hydroxypropofol represents a significant pathway in the metabolism of this anesthetic agent in humans. The aim of this study was to identify the principal cytochrome P-450 (CYP) isoforms mediating this biotransformation. Methods Propofol hydroxylation activities and enzyme kinetics were determined using human liver microsomes and cDNA-expressed CYPs. CYP-specific marker activities and CYP2B6 protein content were also quantified in hepatic microsomes for correlational analyses. Finally, inhibitory antibodies were used to ascertain the relative contribution of CYPs to propofol hydroxylation by hepatic microsomes. Results Propofol hydroxylation by hepatic microsomes showed more than 19-fold variability and was most closely correlated to CYP2B6 protein content (r = 0.904), and the CYP2B6 marker activities, S-mephenytoin N-demethylation (r = 0.919) and bupropion hydroxylation (r = 0.854). High- and intermediate-activity livers demonstrated high-affinity enzyme kinetics (K(m) < 8 microm), whereas low-activity livers displayed low-affinity kinetics (K(m) > 80 microm). All of the CYPs evaluated were capable of hydroxylating propofol; however, CYP2B6 and CYP2C9 were most active. Kinetic analysis indicated that CYP2B6 is a high-affinity (K(m) = 10 +/- 2 microm; mean +/- SE of the estimate), high-capacity enzyme, whereas CYP2C9 is a low-affinity (K(m) = 41 +/- 8 microm), high-capacity enzyme. Furthermore, immunoinhibition showed a greater contribution of CYP2B6 (56 +/- 22% inhibition; mean +/- SD) compared with CYP2C isoforms (16 +/- 7% inhibition) to hepatic microsomal activity. Conclusions Cytochrome P-450 2B6, and to a lesser extent CYP2C9, contribute to the oxidative metabolism of propofol. However, CYP2B6 is the principal determinant of interindividual variability in the hydroxylation of this drug by human liver microsomes.

Sign in / Sign up

Export Citation Format

Share Document