Human N-demethylation of (S)-mephenytoin by cytochrome P450s 2C9 and 2B6.
作者： Jae Wook Ko , David A. Flockhart , Zeruesenay Desta
DOI:
关键词:
摘要: We tested the ability of human liver microsomes (HLMs) and recombinant cytochrome P450 (CYP or P450) isoforms to catalyze N-demethylation nirvanol-free (S)-mephenytoin [(S)-MP] in vitro. In mixed HLMs, kinetics (S)-MPN-demethylation suggested two contributing activities. A high-affinity/low-capacity component exhibited aKM 174.1 μM aVmax 170.5 pmol/mg protein/min, whereas a low-affinity/high-capacity 1911 3984 protein/min. The activity high-affinity was completely abolished by sulfaphenazole, with little effect on low-affinity component. Of tested, only CYP2B6 CYP2C9 formed nirvanol from (S)-MP. KMvalue (150 ± 42 μM) derived for close that obtained HLMs (KM = μM). predicted contribution this at concentrations (1–25 achieved after single 100-mg dose racemic MP is approximately 30% rate formation. At >1000 μM, we estimate >90% can be explained (CYP2B6). Therefore, (S)-MP may useful means probing vitro when are used, but it unlikely suitable phenotyping tool isoform vivo, where rarely encountered.
参考文章(20)
J C Stevens, H Heyn, R B White, Catalytic role of cytochrome P4502B6 in the N-demethylation of S-mephenytoin. Drug Metabolism and Disposition. ,vol. 24, pp. 948- 954 ,(1996)
Allan S. Troupin, Linda Moretti Ojemann, Carl B. Dodrill, Mephenytoin: A Reappraisal Epilepsia. ,vol. 17, pp. 403- 414 ,(1976) , 10.1111/J.1528-1157.1976.TB04452.X
S.A. Wrighton, J.C. Stevens, G.W. Becker, M. Vandenbranden, Isolation and characterization of human liver cytochrome P450 2C19 : correlation between 2C19 and S-mephenytoin 4'-hydroxylation Archives of Biochemistry and Biophysics. ,vol. 306, pp. 240- 245 ,(1993) , 10.1006/ABBI.1993.1506
H.B. Pollard, R. Menard, H.A. Brandt, C.J. Pazoles, C.E. Creutz, A. Ramu, Application of Bradford's protein assay to adrenal gland subcellular fractions Analytical Biochemistry. ,vol. 86, pp. 761- 763 ,(1978) , 10.1016/0003-2697(78)90805-9
Sean Ekins, Mark VandenBranden, Barbara J. Ring, Steven A. Wrighton, Examination of purported probes of human CYP2B6. Pharmacogenetics. ,vol. 7, pp. 165- 179 ,(1997) , 10.1097/00008571-199706000-00001
Ashoke K. Mitra, Kenneth E. Thummel, Thomas F. Kalhorn, Evan D. Kharasch, Jashvant D. Unadkat, John T. Slattery, Inhibition of sulfamethoxazole hydroxylamine formation by fluconazole in human liver microsomes and healthy volunteers* Clinical Pharmacology & Therapeutics. ,vol. 59, pp. 332- 340 ,(1996) , 10.1016/S0009-9236(96)80011-7
Allan S. Troupin, Patrick Friel, Mary Pat Lovely, Alan J. Wilensky, Clinical pharmacology of mephenytoin and ethotoin. Annals of Neurology. ,vol. 6, pp. 410- 414 ,(1979) , 10.1002/ANA.410060506
J. A. Goldstein, M. B. Faletto, M. Romkes-Sparks, T. Sullivan, S. Kitareewan, J. L. Raucy, J. M. Lasker, B. I. Ghanayem, Evidence That CYP2C19 is the Major (S)-Mephenytoin 4'-Hydroxylase in Humans Biochemistry. ,vol. 33, pp. 1743- 1752 ,(1994) , 10.1021/BI00173A017
U.Thomas Meier, Thomas Kronbach, Urs A. Meyer, Assay of mephenytoin metabolism in human liver microsomes by high-performance liquid chromatography Analytical Biochemistry. ,vol. 151, pp. 286- 291 ,(1985) , 10.1016/0003-2697(85)90177-0
P J Wedlund, W S Aslanian, C B McAllister, G R Wilkinson, R A Branch, Mephenytoin hydroxylation deficiency in Caucasians: Frequency of a new oxidative drug metabolism polymorphism Clinical Pharmacology and Therapeutics. ,vol. 36, pp. 773- 780 ,(1984) , 10.1038/CLPT.1984.256