Metabolism of melatonin by cytochrome P450s in rat liver mitochondria and microsomes.
In the present study we provide direct evidence for the involvement of rat microsomal cytochrome P450s in melatonin O-demethylation and hydroxylation at two different positions: 2 and 6, as well as generation of N(1)-acetyl-N(2)-formyl-5-methoxy-kynuramine (AFMK) and two unknown products. Moreover, we found that mitochondrial cytochrome P450s also converts melatonin into AFMK, N-acetylserotonin, 2-hydroxymelatonin, 6-hydroxymelatonin and the same two unknown products. Eadie-Hofstee plots for 6-hydroxylation and O-demethylation reactions were curvilinear for all tested fractions, suggestive of involvement of at least two components, one with a high affinity and low capacity, and another with a low affinity and high capacity. Mitochondrial cytochrome P450s exhibited higher affinity (suggesting lower K(m) value) and higher V(max) for melatonin 6-hydroxylation and O-demethylation for both high-affinity and low-affinity components as compared with microsomal enzymes. The intrinsic clearance for melatonin hydroxylation by high- and low-affinity components displayed the highest values in all tested fractions, indicating that both mitochondrial and microsomal cytochrome P450s metabolize melatonin principally by 6-hydroxylation, with O-demethylation representing a minor metabolic pathway.
Semak
Igor
I
Department of Biochemistry, Belarus State University, Minsk, Belarus.
Korik
Elena
E
Antonova
Maria
M
Wortsman
Jacobo
J
Slominski
Andrzej
A
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D007700:Kinetics; D007735:Kynuramine / Q000031:analogs & derivatives / Q000378:metabolism; D008099:Liver; D008297:Male; D008550:Melatonin / Q000031:analogs & derivatives / Q000378:metabolism*; D008862:Microsomes, Liver / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000031:analogs & derivatives / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization
D065607:Cytochrome P-450 Enzyme Inhibitors; C487380:N-(2-(5-methoxy-2-oxo-2,3-dihydro-1H-indol-3-yl)ethyl)acetamide; D012701:Serotonin; D007735:Kynuramine; C041550:N-acetyl-N-formyl-5-methoxykynurenamine; D003577:Cytochrome P-450 Enzyme System; D008550:Melatonin; C006389:N-acetylserotonin; C012365:6-hydroxymelatonin