Hadley M R, Oldham H G, Damani L A, Hutt A J
Department of Pharmacy, King's College London, England.
Chirality. 1994;6(2):98-104. doi: 10.1002/chir.530060210.
The prochiral tertiary amine N-ethyl-N-methylaniline (EMA) is known to be metabolically N-oxygenated in vitro with microsomal preparations. This biotransformation is thought to be mediated predominantly by the flavin-containing monooxygenase (FMO) enzyme system. Microsomal N-oxygenation of EMA is known to be stereoselective and varies between species. In order to further characterise this metabolic transformation, we have examined the in vitro metabolism of EMA using purified porcine hepatic FMO. Following incubation of EMA with purified FMO, EMA N-oxide, the only metabolic detected, was found to be produced stereoselectively [ratio (-)-(S):(+)-(R), ca. 4:1]. The enantiomeric ratio of the N-oxide product did not change markedly with respect to time, enzyme or substrate concentration. Determination of the kinetics of formation of the N-oxide indicated a single affinity for the prochiral substrate with differential rates of formation of the enantiomers. The extent of EMA N-oxide formation was shown to be affected by activators and inhibitors of FMO and pH, but its stereoselectively was unaltered.
前手性叔胺N-乙基-N-甲基苯胺（EMA）在体外经微粒体制剂代谢会发生N-氧化。这种生物转化被认为主要由含黄素单加氧酶（FMO）酶系统介导。已知EMA的微粒体N-氧化具有立体选择性，且在不同物种之间存在差异。为了进一步表征这种代谢转化，我们使用纯化的猪肝FMO研究了EMA的体外代谢。将EMA与纯化的FMO孵育后，发现唯一检测到的代谢产物EMA N-氧化物是立体选择性产生的[对映体比例（-）-（S）：（+）-（R），约4:1]。N-氧化物产物的对映体比例随时间、酶或底物浓度没有明显变化。对N-氧化物形成动力学的测定表明，前手性底物具有单一亲和力，对映体形成速率不同。结果表明，EMA N-氧化物的形成程度受FMO的激活剂和抑制剂以及pH的影响，但其立体选择性未改变。
