title: Human liver microsomal cytochrome P450 3A enzymes involved in thalidomide 5-hydroxylation and formation of a glutathione conjugate.
abstract: (R)-Thalidomide was oxidized to 5-hydroxythalidomide and 5'-hydroxythalidomide by NADPH-fortified liver microsomes from humans and monkeys. (R)-Thalidomide was hydroxylated more efficiently than (S)-thalidomide. Recombinant human P450s 3A4, 3A5, and 3A7 and monkey P450s 3A8 and 3A5 (coexpressed with NADPH-P450 reductase in bacterial membranes) also catalyzed (R)-thalidomide 5-hydroxylation. Purified human P450s 2C19, 3A4, and 3A5 mediated (R)-thalidomide 5-hydroxylation at similar rates in reconstituted systems. P450 2C19 showed a rather nonsaturable substrate-velocity curve; however, P450s 3A4 and 3A5 showed sigmoidal curves. P450 also oxidized 5-hydroxythalidomide to an epoxide or dihydroxy compound. Liquid chromatography-mass spectrometry analysis revealed the formation of a glutathione conjugate from (R)- and (S)-5-hydroxythalidomide, catalyzed by liver microsomal P450s 3A4 and 3A5 in the presence of glutathione (assigned as a conjugate of 5-hydroxythalidomide formed on the phenyl ring). These results indicate that human P450s 3A4 and 3A5 mediate thalidomide 5-hydroxylation and further oxidation leading to a glutathione conjugate, which may be of relevance in the pharmacological and toxicological actions of thalidomide.
authors.affiliation: Laboratory of Drug Metabolism and Pharmacokinetics, Showa Pharmaceutical University, Machida, Tokyo 194-8543, Japan.
authors.forename: Goutam
authors.initials: G
authors.lastname: Chowdhury
authors.forename: Norie
authors.initials: N
authors.lastname: Murayama
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Okada
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Uno
authors.forename: Makiko
authors.initials: M
authors.lastname: Shimizu
authors.forename: Norio
authors.initials: N
authors.lastname: Shibata
authors.forename: F Peter
authors.initials: FP
authors.lastname: Guengerich
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamazaki
mesh_terms: D000818:Animals; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D006900:Hydroxylation; D008252:Macaca fascicularis; D008862:Microsomes, Liver / Q000201:enzymology*; D010084:Oxidation-Reduction; D011817:Rabbits; D013552:Swine; D013792:Thalidomide / Q000378:metabolism*
chemical_list: D013792:Thalidomide; D051544:Cytochrome P-450 CYP3A; D005978:Glutathione