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目的:研究普罗帕酮(PPF)经人肝CYP3A4代谢的立体选择性。方法:以转人肝CYP3A4基因中国仓鼠肺细胞CHL的S_9为酶源,考察了PPF消旋体及单个对映体在高、低底物浓度时的经时孵育代谢。对映体抑制试验用于考察对映体之间的相互作用。并进行了单个对映体的酶动力学试验。结果:PPF消旋体高底物浓度(400mg/L)时的代谢无立体选择性,低底物浓度(10mg/L)时R(-)-体代谢快于S(+)-体(R>S);单个对映体孵育时在高底物浓度(200mg/L)时的代谢呈现对S(+)-体的立体选择性(S>R),低底物浓度(5mg/L)时呈现对R(-)-体的立体选择性(R>S)。S(+)-PPF的V_(max)(μmol·mg~(-1)·min~(-1))大于R(-)-体(2.66±0.32 vs 1.71±0.19,P<0.01)。R(-)-PPF的K_m(μmol·L~(-1))小于S(+)-体(73±11 vs 185±17,P<0.001)。R(-)-PPF对S(+)-体有代谢抑制作用(IC_(50)=125μmol·L~(-1))。结论:PPF经人肝CYP3A4的代谢有底物浓度依赖性的立体选择性。高底物浓度时两对映体有相互作用,相互作用的结果导致立体选择性丧失。而低底物浓度时两对映体无相互作用,结果仍表现出R体代谢优先的立体选择性。
Objective: To study the stereoselectivity of propafenone (PPF) metabolism in human liver CYP3A4. Methods: S_9 of CHL from human hamster lung cells transfected with human liver CYP3A4 gene was used as enzyme source to investigate the time-dependent metabolism of PPF racemate and single enantiomer at high and low substrate concentrations. Enantiomeric inhibition tests were used to investigate the enantiomeric interactions. Enzymatic kinetics of individual enantiomers was performed. Results: Metabolism of PPF racemate at high substrate concentration (400mg / L) was not stereoselective. At low substrate concentration (10mg / L), R (-) - (S> R) at low substrate concentration (5 mg / L) when the single enantiomer was incubated at a high substrate concentration (200 mg / L) Stereoselectivity to R (-) - body was presented (R> S). The V max (μmol · mg -1 · min -1) of S (+) - PPF was higher than that of R (-) - (2.66 ± 0.32 vs 1.71 ± 0.19, P <0.01). The K_m (μmol·L -1) of R (-) - PPF was smaller than that of S (+) - (73 ± 11 vs 185 ± 17, P <0.001). R (-) - PPF inhibited the metabolism of S (+) - (IC 50 = 125μmol·L -1). CONCLUSION: The metabolism of PPF via human liver CYP3A4 has substrate-concentration-dependent stereoselectivity. The two enantiomers interact at high substrate concentrations, and the interaction results in a loss of stereoselectivity. However, there was no interaction between the two enantiomers at low substrate concentrations, and the results still showed stereoselectivity of R metabolism priority.