Linked Life Data

8886603

Source:http://linkedlifedata.com/resource/pubmed/id/8886603

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
9
pubmed:dateCreated
1997-2-12
pubmed:abstractText
In vitro methods were used to identify the cytochrome P450 (CYP) enzyme(s) involved in S-mephenytoin N-demethylation. S-Mephenytoin (200 microM) was incubated with human liver microsomes, and nirvanol formation was quantitated by reversed-phase HPLC. S-Mephenytoin N-demethylase activity in a panel of human liver microsomes ranged 35-fold from 9 to 319 pmol/min/mg protein and correlated strongly with microsomal CYP2B6 activity (r = 0.91). Additional correlations were found with microsomal CYP2A6 and CYP3A4 activity (r = 0.88 and 0.74, respectively). Microsomes prepared from human beta-lymphoblastoid cells transformed with individual P450 cDNAs were assayed for S-mephenytoin N-demethylase activity. Of 11 P450 isoforms (P450s 1A1, 1A2, 2A6, 2B6, 2E1, 2D6, 2C8, 2C9, 2C19, 3A4, and 3A5) tested, only CYP2B6 catalyzed the N-demethylation of S-mephenytoin with an apparent K(m) of 564 microM. Experiments with P450 form-selective chemical inhibitors, competitive substrates, and anti-P450 antibodies were also performed. Troleandomycin, a mechanism-based CYP3A selective inhibitor, and coumarin, a substrate for CYP2A6 and therefore a potential competitive inhibitor, failed to inhibit human liver microsomal S-mephenytoin N-demethylation. In contrast, orphenadrine, an inhibitor of CYP2B forms, produced a 51 +/- 4% decrease in S-mephenytoin N-demethylase activity in human liver microsomes and a 45% decrease in recombinant microsomes expressing CYP2B6. Also, both CYP2B6-marker 7-ethoxytrifluoromethylcoumarin O-deethylase and S-mephenytoin N-demethylase activities were inhibited by approximately 65% by 5 mg anti-CYP2B1 IgG/mg microsomal protein. Finally, polyclonal antibody inhibitory to CYP3A1 failed to inhibit S-mephenytoin N-demethylase activity. Taken together, these studies indicate that the N-demethylation of S-mephenytoin by human liver microsomes is catalyzed primarily by CYP2B6.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
http://linkedlifedata.com/resource/pubmed/chemical/Antibodies, Monoclonal, http://linkedlifedata.com/resource/pubmed/chemical/Anticonvulsants, http://linkedlifedata.com/resource/pubmed/chemical/Aryl Hydrocarbon Hydroxylases, http://linkedlifedata.com/resource/pubmed/chemical/CYP3A protein, human, http://linkedlifedata.com/resource/pubmed/chemical/CYP3A4 protein, human, http://linkedlifedata.com/resource/pubmed/chemical/Coumarins, http://linkedlifedata.com/resource/pubmed/chemical/Cytochrome P-450 CYP3A, http://linkedlifedata.com/resource/pubmed/chemical/Cytochrome P-450 Enzyme System, http://linkedlifedata.com/resource/pubmed/chemical/Isoenzymes, http://linkedlifedata.com/resource/pubmed/chemical/Mephenytoin, http://linkedlifedata.com/resource/pubmed/chemical/Mixed Function Oxygenases, http://linkedlifedata.com/resource/pubmed/chemical/Oxidoreductases, N-Demethylating, http://linkedlifedata.com/resource/pubmed/chemical/Recombinant Proteins, http://linkedlifedata.com/resource/pubmed/chemical/Troleandomycin, http://linkedlifedata.com/resource/pubmed/chemical/coumarin, http://linkedlifedata.com/resource/pubmed/chemical/coumarin 7-hydroxylase, http://linkedlifedata.com/resource/pubmed/chemical/ethylphenylhydantoin
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
0090-9556
pubmed:author
pubmed:issnType
Print
pubmed:volume
24
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
948-54
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed:year
1996
pubmed:articleTitle
Catalytic role of cytochrome P4502B6 in the N-demethylation of S-mephenytoin.
pubmed:affiliation
Department of Drug Metabolism and Pharmacokinetics, Rhône-Poulenc Rorer Research and Development, Collegeville, PA 19426-0107, USA.
pubmed:publicationType
Journal Article