Oxidative metabolism of 5-methoxy-N,N-diisopropyltryptamine (Foxy) by human liver microsomes and recombinant cytochrome P450 enzymes.
In vitro quantitative studies of the oxidative metabolism of (5-methoxy-N,N-diisopropyltryptamine, 5-MeO-DIPT, Foxy) were performed using human liver microsomal fractions and recombinant CYP enzymes and synthetic 5-MeO-DIPT metabolites. 5-MeO-DIPT was mainly oxidized to O-demethylated (5-OH-DIPT) and N-deisopropylated (5-MeO-IPT) metabolites in pooled human liver microsomes. In kinetic studies, 5-MeO-DIPT O-demethylation showed monophasic kinetics, whereas its N-deisopropylation showed triphasic kinetics. Among six recombinant CYP enzymes (CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6 and CYP3A4) expressed in yeast or insect cells, only CYP2D6 exhibited 5-MeO-DIPT O-demethylase activity, while CYP1A2, CYP2C8, CYP2C9, CYP2C19 and CYP3A4 showed 5-MeO-DIPT N-deisopropylase activities. The apparent Km value of CYP2D6 was close to that for 5-MeO-DIPT O-demethylation, and the Km values of other CYP enzymes were similar to those of the low-Km (CYP2C19), intermediate-Km (CYP1A2, CYP2C8 and CYP3A4) and high-Km phases (CYP2C9), respectively, for N-deisopropylation in human liver microsomes. In inhibition studies, quinidine (1 microM), an inhibitor of CYP2D6, almost completely inhibited human liver microsomal 5-MeO-DIPT O-demethylation at a substrate concentration of 10 microM. Furafylline, a CYP1A2 inhibitor, quercetin, a CYP2C8 inhibitor, sulfaphenazole, a CYP2C9 inhibitor and ketoconazole, a CYP3A4 inihibitor (5 microM each) suppressed about 60%, 45%, 15% and 40%, respectively, of 5-MeO-DIPT N-deisopropylation at 50 microM substrate. In contrast, omeprazole (10 microM), a CYP2C19 inhibitor, suppressed only 10% of N-deisopropylation by human liver microsomes, whereas at the same concentration the inhibitor suppressed the reaction by recombinant CYP2C19 almost completely. These results indicate that CYP2D6 is the major 5-MeO-DIPT O-demethylase, and CYP1A2, CYP2C8 and CYP3A4 are the major 5-MeO-DIPT N-deisopropylase enzymes in the human liver.
Narimatsu
Shizuo
S
Laboratory of Health Chemistry, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-naka, Okayama 700-8530, Japan. shizuo@pharm.okayama-u.ac.jp
Yonemoto
Rei
R
Saito
Keita
K
Takaya
Kazuo
K
Kumamoto
Takuya
T
Ishikawa
Tsutomu
T
Asanuma
Masato
M
Funada
Masahiko
M
Kiryu
Kimio
K
Naito
Shinsaku
S
Yoshida
Yuzo
Y
Yamamoto
Shigeo
S
Hanioka
Nobumitsu
N
D008735:5-Methoxytryptamine / Q000031:analogs & derivatives* / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008862:Microsomes, Liver / Q000201:enzymology*; D010084:Oxidation-Reduction; D011994:Recombinant Proteins / Q000378:metabolism
D011994:Recombinant Proteins; C033696:5-methoxy-N,N-diisopropyltryptamine; D008735:5-Methoxytryptamine; D003577:Cytochrome P-450 Enzyme System